Alumina-zirconia, and methods of making and using the same

ABSTRACT

Alumina-zirconia materials and methods of making the same. Embodiments of the invention include abrasive particles. The abrasive particles can be incorporated into a variety of abrasive articles, including bonded abrasives, coated abrasives, nonwoven abrasives, and abrasive brushes.

This application is a continuation-in-part of U.S. Ser. Nos. 09/922,526,09/922,527, 09/922,528, and 09/922,530, filed Aug. 2, 2001, all nowabandoned, the disclosures of which are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to alumina-zirconia materials.

DESCRIPTION OF RELATED ART

Alumina-zirconia ceramic materials (including stabilized zirconias) suchas alumina-toughened zirconia, zirconia-toughened alumina,alumina-zirconia eutectics are known to have very desirable propertiessuch as high strength, toughness, hardness, high temperature creepresistance, and chemical inertness. It is also known to modifyproperties of alumina-zirconia materials by additions of metal oxides,nitrides, and carbides.

Such alumina-zirconia and alumina-zirconia-based ceramics have beenfabricated into forms such as particles, coatings, fibers, and bulkmaterials. Known uses of such materials include fillers, abrasiveparticles, cutting tool inserts, grinding media, refractories, fibers,thermal-barrier, abrasion, and corrosion resistant coatings.

Methods for making known bulk alumina-zirconia andalumina-zirconia-based ceramics include powder coalescence (i.e., bysintering, hot pressing, HIPing, etc.) techniques, sol-gel processing,fusion, and plasma processing such as plasma spraying. Methods formaking known alumina-zirconia and alumina-zirconia-based ceramics inparticulate form include crushing the bulk materials and atomizationtechniques for making spherical particles. The form of thealumina-zirconia and alumina-zirconia-based in terms of being amorphous,crystalline, or a combination thereof, and for crystalline materials,the particular microstructure, may depend for a given composition, forexample, on the processing method and processing conditions.

Forms of amorphous or partially amorphous alumina-zirconia made byfusion processing rapidly quenching a melt or other (such as atomizationand plasma processing) are known. Formation of predominantly amorphousalumina-zirconia powders by spray pyrolysis of salts is also known.

Further, although many metal oxides can be obtained in an amorphous(including glassy) state by melting and rapidly quenching, most, becauseof the need for very high quench rates to provide amorphous material,tend to form crystalline material if the size of the material is toolarge. Hence many cannot be formed into bulk or complex shapes.Generally, such systems are very unstable against crystallization duringsubsequent reheating and therefore do not exhibit such properties asviscous flow.

On the other hand, glasses based on the conventional network formingoxides (e.g., silica and boria) are generally relatively stable againstcrystallization during reheating and, correspondingly, the “working”range where viscous flow occurs can readily be accessed. Formation oflarge articles from powders of known glass (e.g., silica and boria) viaviscous sintering at temperatures above glass transition temperature iswell known. For example, in the abrasive industry, grinding wheels aremade using vitrified bond to secure abrasive particles together.

Although amorphous and crystalline forms of alumina-zirconia are known,new forms and/or alumina-zirconia compositions are desirable,particularly those that in are or can be used to make useful (bulk)articles or abrasive particles.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides amorphous materialcomprising Al₂O₃ (in some embodiments preferably, at least 20, 25, 30,35, 40, 45, 50, 55, 60, 65, or even, at least 70 percent by weightAl₂O₃, based on the total weight of the amorphous material), ZrO₂ (insome embodiments preferably, at least 15, 20, 25, 30, 35, 40, or even,at least 45 percent by weight ZrO₂, based on the total weight of theamorphous material), and a metal oxide other than Al₂O₃ or ZrO₂ (e.g.,Y₂O₃, REO, TiO₂, CaO, Cr₂O₃, MgO, NiO, CuO, and complex metal oxidesthereof), wherein at least a portion of the metal oxide other than Al₂O₃or ZrO₂ forms a distinct crystalline phase when the amorphous materialis crystallized, wherein the amorphous material comprises at least 50(in some embodiments preferably, at least 55, 60, 65, 70, 75, 80, 85,90, or even 95) percent by weight collectively of the Al₂O₃ and theZrO₂, based on the total weight of the amorphous material, wherein theamorphous material contains not more than 20 (in some embodiments,preferably not more than 15, 10, 5, 4, 3, 2, 1, or zero) percent byweight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, basedon the total weight of the amorphous material, wherein the amorphousmaterial has x, y, and z dimensions each perpendicular to each other,and wherein each of the x, y, and z dimensions is at least 25micrometers (in some embodiments, preferably, at least 30 micrometers,35 micrometers, 40 micrometers, 45 micrometers, 50 micrometers, 75micrometers, 100 micrometers, 150 micrometers, 200 micrometers, 250micrometers, 500 micrometers, 1000 micrometers, 2000 micrometers, 2500micrometers, 1 mm, 5 mm, or even at least 10 mm).

In another aspect, the present invention provides a method for makingamorphous material according to the present invention. The methodcomprising melting sources of at least Al₂O₃, ZrO₂, and a metal oxideother than Al₂O₃ or ZrO₂ to provide a melt; and cooling the melt toprovide the amorphous material.

A “distinct crystalline phase” is a crystalline phase (including acrystalline complex metal oxide) that is detectable by x-ray diffractionas opposed to a phase that is present in solid solution with anotherdistinct crystalline phase. For example, it is well known that oxidessuch as Y₂O₃ or CeO₂ may be in solid solution with a crystalline ZrO₂and serve as a phase stabilizer. The Y₂O₃ or CeO₂ in such instances isnot a distinct crystalline phase.

The x, y, and z dimensions of a material are determined either visuallyor using microscopy, depending on the magnitude of the dimensions. Thereported z dimension is, for example, the diameter of a sphere, thethickness of a coating, or the longest length of a prismatic shape.

In this application:

“amorphous material” refers to material derived from a melt and/or avapor phase that lacks any long range crystal structure as determined byX-ray diffraction and/or has an exothermic peak corresponding to thecrystallization of the amorphous material as determined by a DTA(differential thermal analysis) as determined by the test describedherein entitled “Differential Thermal Analysis”;

“ceramic” includes amorphous material, glass, crystalline ceramic,glass-ceramic, and combinations thereof;

“complex metal oxide” refers to a metal oxide comprising two or moredifferent metal elements and oxygen (e.g., CeAl₁₁O₁₈, Dy₃Al₅O₁₂,MgAl₂O₄, and Y₃Al₅O₁₂);

“complex Al₂O₃.metal oxide” refers to a complex metal oxide comprising,on a theoretical oxide basis, Al₂O₃ and one or more metal elements otherthan Al (e.g., CeAl₁₁O₁₈, Dy₃Al₅O₁₂, MgAl₂O₄, and Y₃Al₅O₁₂);

“complex Al₂O₃.Y₂O₃” refers to a complex metal oxide comprising, on atheoretical oxide basis, Al₂O₃ and Y₂O₃ (e.g., Y₃Al₅O₁₂);

“complex Al₂O₃.REO” refers to a complex metal oxide comprising, on atheoretical oxide basis, Al₂O₃ and rare earth oxide (e.g., CeAl₁₁O₁₈ andDy₃Al₅O₁₂);

“glass” refers to amorphous material exhibiting a glass transitiontemperature;

“glass-ceramic” refers to ceramic comprising crystals formed byheat-treating amorphous material;

“T_(g)” refers to the glass transition temperature as determined by thetest described herein entitled “Differential Thermal Analysis”;

“T_(x)” refers to the crystallization temperature as determined by thetest described herein entitled “Differential Thermal Analysis”;

“rare earth oxides” refers to cerium oxide (e.g., CeO₂), dysprosiumoxide (e.g., Dy₂O₃), erbium oxide (e.g., Er₂O₃), europium oxide (e.g.,Eu₂O₃), gadolinium (e.g., Gd₂O₃), holmium oxide (e.g., Ho₂O₃), lanthanumoxide (e.g., La₂O₃), lutetium oxide (e.g., Lu₂O₃), neodymium oxide(e.g., Nd₂O₃), praseodymium oxide (e.g., Pr₆O₁₁), samarium oxide (e.g.,Sm₂O₃), terbium (e.g., Tb₂O₃), thorium oxide (e.g., Th₄O₇), thulium(e.g., Tm₂O₃), and ytterbium oxide (e.g., Yb₂O₃), and combinationsthereof; and

“REO” refers to rare earth oxide(s).

Further, it is understood herein that unless it is stated that a metaloxide (e.g., Al₂O₃, complex Al₂O₃.metal oxide, etc.) is crystalline, forexample, in a glass-ceramic, it may be amorphous, crystalline, orportions amorphous and portions crystalline. For example if aglass-ceramic comprises Al₂O₃ and ZrO₂, the Al₂O₃ and ZrO₂ may each bein an amorphous state, crystalline state, or portions in an amorphousstate and portions in a crystalline state, or even as a reaction productwith another metal oxide(s) (e.g., unless it is stated that, forexample, Al₂O₃ is present as crystalline Al₂O₃ or a specific crystallinephase of Al₂O₃ (e.g., alpha Al₂O₃), it may be present as crystallineAl₂O₃ and/or as part of one or more crystalline complex Al₂O₃.metaloxides.

Further, it is understood that glass-ceramics formed by heatingamorphous material not exhibiting a T_(g) may not actually compriseglass, but rather may comprise the crystals and amorphous material thatdoes not exhibiting a T_(g).

In one aspect, the present invention provides glass-ceramic comprisingAl₂O₃ (in some embodiments preferably, at least 20, 25, 30, 35, 40, 45,50, 55, 60, 65, or even, at least 70 percent by weight Al₂O₃, based onthe total weight of the glass-ceramic), ZrO₂ (in some embodimentspreferably, at least 15, 20, 25, 30, 35, 40, or even, at least 45percent by weight ZrO₂, based on the total weight of the glass-ceramic),and a metal oxide other than Al₂O₃ or ZrO₂ (e.g., Y₂O₃, REO, TiO₂, CaO,Cr₂O₃, MgO, NiO, CuO, and complex metal oxides thereof), wherein atleast a portion of the metal oxide other than Al₂O₃ or ZrO₂ is presentas at least one distinct crystalline phase, wherein the glass-ceramiccomprises at least 50 (in some embodiments preferably, at least 55, 60,65, 70, 75, 80, 85, 90, or even 95) percent by weight collectively ofthe Al₂O₃ and the ZrO₂, based on the total weight of the glass-ceramic,wherein the glass-ceramic contains not more than 20 (in someembodiments, preferably not more than 15, 10, 5, 4, 3, 2, 1, or zero)percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the glass-ceramic, wherein theglass-ceramic has x, y, and z dimensions each perpendicular to eachother, and wherein each of the x, y, and z dimensions is at least 25micrometers (in some embodiments, preferably, at least 30 micrometers,35 micrometers, 40 micrometers, 45 micrometers, 50 micrometers, 75micrometers, 100 micrometers, 150 micrometers, 200 micrometers, 250micrometers, 500 micrometers, 1000 micrometers, 2000 micrometers, 2500micrometers, 1 mm, 5 mm, or even at least 10 mm).

In some embodiments, the amorphous material may present in anothermaterial (e.g., particles comprising the amorphous material according tothe present invention, ceramic comprising the amorphous materialaccording to the present invention, etc.). Optionally, the amorphousmaterial (including a glass) is heat-treated such that at least aportion of the amorphous material is converted to a glass-ceramic.

In one aspect, the present invention provides abrasive particlesaccording to the present invention comprise a glass-ceramic. Someembodiments of abrasive particles according to the present inventioncomprise a glass-ceramic, wherein the glass-ceramic comprises Al₂O₃ (insome embodiments preferably, at least 20, 25, 30, 35, 40, 45, 50, 55,60, 65, or even, at least 70 percent by weight Al₂O₃, based on the totalweight of the glass-ceramic), at least 15 (in some embodimentspreferably, at least 20, 25, 30, 35, 40, or even, at least 45 percent byweight ZrO₂, based on the total weight of the glass-ceramic), and Y₂O₃(in some embodiments preferably, at least 0.5 to 15%, more preferably 1to 10 percent by weight Y₂O₃, based on the total weight of theglass-ceramic), wherein at least a portion of the Y₂O₃ is present as atleast one distinct crystalline phase (e.g., crystalline Y₂O₃ and/orcrystalline complex Y₂O₃.metal oxide).

Some embodiments of abrasive particles according to the presentinvention comprise a glass-ceramic, wherein the glass-ceramic comprisesAl₂O₃ (in some embodiments preferably, at least 20, 25, 30, 35, 40, 45,50, 55, 60, 65, or even, at least 70 percent by weight Al₂O₃, based onthe total weight of the glass-ceramic), at least 15 (in some embodimentspreferably, at least 20, 25, 30, 35, 40, or even, at least 45 percent byweight ZrO₂, based on the total weight of the glass-ceramic, and REO (insome embodiments preferably, at least 0.5 to 15%, more preferably 1 to10 percent by weight REO, based on the total weight of theglass-ceramic), wherein at least a portion of the REO is present as atleast one distinct crystalline phase (e.g., crystalline REO and/orcrystalline complex REO.metal oxide).

Some embodiments of abrasive particles according to the presentinvention comprise a glass-ceramic, wherein the glass-ceramic comprisesAl₂O₃ (in some embodiments preferably, at least 20, 25, 30, 35, 40, 45,50, 55, 60, 65, or even, at least 70 percent by weight Al₂O₃, based onthe total weight of the amorphous material), at least 15 (in someembodiments preferably, at least 20, 25, 30, 35, 40, 45, or even, atleast 45) percent by weight ZrO₂, based on the total weight of theglass-ceramic, and contains not more than 10 (in some embodiments,preferably not more than 5, 4, 3, 2, 1, or zero) percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the glass-ceramic, wherein the glass-ceramic has x, y,and z dimensions each perpendicular to each other, and wherein each ofthe x, y, and z dimensions is at least 25 micrometers.

Some embodiments of abrasive particles according to the presentinvention comprise a glass-ceramic, wherein the glass-ceramic comprisesAl₂O₃ (in some embodiments preferably, at least 20, 25, 30, 35, 40, 45,50, 55, 60, 65, or even, at least 70 percent by weight Al₂O₃, based onthe total weight of the glass-ceramic), ZrO₂ (in some embodimentspreferably, at least 20, 25, 30, 35, 40, or even, at least 45 percent byweight ZrO₂, based on the total weight of the glass-ceramic), and ametal oxide other than Al₂O₃ or ZrO₂ (e.g., Y₂O₃, REO, TiO₂, CaO, Cr₂O₃,MgO, NiO, CuO, and complex metal oxides thereof), wherein at least aportion of the metal oxide other than Al₂O₃ or ZrO₂ is present as atleast one distinct crystalline phase, wherein the glass-ceramiccollectively comprises at least 50 (in some embodiments preferably, atleast 55, 60, 65, 70, 75, 80, 85, 90, or even 95) percent by weightcollectively of the Al₂O₃ and the ZrO₂, based on the total weight of theglass-ceramic, wherein the glass-ceramic contains not more than 20 (insome embodiments, preferably not more than 15, 10, 5, 4, 3, 2, 1, orzero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂,TeO₂, and V₂O₅, based on the based on the total weight of theglass-ceramic.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising:

-   -   heat-treating amorphous material (including a glass) such that        at least a portion of the amorphous material is converted to a        glass-ceramic; and    -   crushing the glass-ceramic to provide abrasive particles        comprising the glass-ceramic.

The abrasive particles can be incorporated into an abrasive article, orused in loose form. Abrasive articles according to the present inventioncomprise binder and a plurality of abrasive particles, wherein at leasta portion of the abrasive particles are the abrasive particles accordingto the present invention. Exemplary abrasive products include coatedabrasive articles, bonded abrasive articles (e.g., wheels), non-wovenabrasive articles, and abrasive brushes. Coated abrasive articlestypically comprise a backing having first and second, opposed majorsurfaces, and wherein the binder and the plurality of abrasive particlesform an abrasive layer on at least a portion of the first major surface.

In some embodiments, preferably, at least 5, 10, 15, 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or even 100 percent byweight of the abrasive particles in an abrasive article are the abrasiveparticles according to the present invention, based on the total weightof the abrasive particles in the abrasive article.

Abrasive particles are usually graded to a given particle sizedistribution before use. Such distributions typically have a range ofparticle sizes, from coarse particles fine particles. In the abrasiveart this range is sometimes referred to as a “coarse”, “control” and“fine” fractions. Abrasive particles graded according to industryaccepted grading standards specify the particle size distribution foreach nominal grade within numerical limits. Such industry acceptedgrading standards (i.e., specified nominal grades) include those knownas the American National Standards Institute, Inc. (ANSI) standards,Federation of European Producers of Abrasive Products (FEPA) standards,and Japanese Industrial Standard (JIS) standards. In one aspect, thepresent invention provides a plurality of abrasive particles having aspecified nominal grade, wherein at least a portion of the plurality ofabrasive particles are abrasive particles according to the presentinvention. In some embodiments, preferably, at least 5, 10, 15, 20, 25,30, 35, 40, 45, 50 55, 60, 65, 70, 75, 80, 85, 90, 95, or even 100percent by weight of the plurality of abrasive particles are theabrasive particles according to the present invention, based on thetotal weight of the plurality of abrasive particles.

In another aspect, the present invention provides a method for makingabrasive particles according to the present invention, the methodcomprising heat-treating particles comprising the amorphous material(including glass) such that at least a portion of the amorphous materialconverts to a glass-ceramic provide the abrasive particles comprisingthe glass-ceramic. Typically, the abrasive particles comprising theglass-ceramic are graded after heat-treating to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic. Optionally, prior tothe heat-treating the particles the amorphous material, a plurality ofparticles having a specified nominal grade is provided, wherein at leasta portion of the particles is a plurality of the particles comprisingthe amorphous material to be heat-treated, and wherein the heat-treatingis conducted such that a plurality of abrasive particles having aspecified nominal grade is provided, wherein at least a portion of theabrasive particles is a plurality of the abrasive particles comprisingthe glass-ceramic.

In another aspect, the present invention provides a method for makingabrasive particles according to the present invention, the methodcomprising heat-treating particles comprising the amorphous materialsuch that at least a portion of the amorphous material converts to aglass-ceramic to provide the abrasive particles comprising theglass-ceramic. Typically, the abrasive particles comprising theglass-ceramic are graded after heat-treating to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic. Optionally, prior tothe heat-treating the particles comprising the amorphous material, aplurality of particles having a specified nominal grade is provided,wherein at least a portion of the particles is a plurality of theparticles comprising the amorphous material to be heat-treated, andwherein the heat-treating is conducted such that a plurality of abrasiveparticles having a specified nominal grade is provided, wherein at leasta portion of the abrasive particles is a plurality of the abrasiveparticles comprising the glass-ceramic.

Amorphous materials and glass-ceramics according to the presentinvention can be made, formed as, or converted into particles (e.g.,glass beads (e.g., beads having diameters of at least 1 micrometers, 5micrometers, 10 micrometers, 25 micrometers, 50 micrometers, 100micrometers, 150 micrometers, 250 micrometers, 500 micrometers, 750micrometers, 1 mm, 5 mm, or even at least 10 mm)), articles (e.g.,plates), fibers, particles, and coatings (e.g., thin coatings).Amorphous materials and/or glass-ceramic particles and fibers areuseful, for example, as thermal insulation, filler, or reinforcingmaterial in composites (e.g., ceramic, metal, or polymeric matrixcomposites). The thin coatings can be useful, for example, as protectivecoatings in applications involving wear, as well as for thermalmanagement. Examples of articles according of the present inventioninclude kitchenware (e.g., plates), dental brackets, and reinforcingfibers, cutting tool inserts, abrasive materials, and structuralcomponents of gas engines, (e.g., valves and bearings). Other articlesinclude those having a protective coating of ceramic on the outersurface of a body or other substrate.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary cross-sectional schematic view of a coatedabrasive article including abrasive particles according to the presentinvention;

FIG. 2 is a perspective view of a bonded abrasive article includingabrasive particles according to the present invention;

FIG. 3 is an enlarged schematic view of a nonwoven abrasive articleincluding abrasive particles according to the present invention;

FIG. 4 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 1;

FIG. 5 is a Scanning Electron Micrograph (SEM) of fractured surface ofmaterial prepared in Example 3;

FIG. 6 is a DTA curve of Example 22 material;

FIGS. 7–8 are DTA curves of materials prepared in Examples 23 and 24,respectively;

FIG. 9 is an optical photomicrograph of a section of Example 32hot-pressed material;

FIG. 10 is an SEM photomicrograph of a polished cross-section ofheat-treated Example 32 material;

FIG. 11 is an DTA curve of Example 32 material; and

FIG. 12 is an SEM photomicrograph of a polished cross-section of Example52 material.

DETAILED DESCRIPTION

Some embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. include thosecomprising Al₂O₃ (in some embodiments preferably, at least 20, 25, 30,35, 40, 45, 50, 55, 60, 65, or even at least 70 percent by weight Al₂O₃,based on the total weight of the amorphous material or glass-ceramic, asapplicable), ZrO₂ (in some embodiments preferably, at least 15, 20, 25,30, 35, 40, or even at least 45 percent by weight ZrO₂, based on thetotal weight of the amorphous material or glass-ceramic, as applicable),and a metal oxide other than Al₂O₃ or ZrO₂ (e.g., Y₂O₃, REO, MgO, TiO₂,NiO, CaO, Cr₂O₃, CuO and complex metal oxides thereof), wherein at leasta portion of the metal oxide other than Al₂O₃ or ZrO₂ forms a distinctcrystalline phase during heat-treating, wherein the amorphous materialor glass-ceramic, as applicable, comprises at least 50 (in someembodiments preferably, at least 55, 60, 65, 70, 75, 80, 85, 90, or even95) percent by weight collectively of the Al₂O₃ and the ZrO₂, based onthe total weight of the amorphous material or glass-ceramic, asapplicable, wherein the amorphous material or glass-ceramic, asapplicable, contains not more than 20 (in some embodiments, preferablynot more than 15, 10, 5, 4, 3, 2, 1, or zero) percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thebased on the total weight of the amorphous material or glass-ceramic, asapplicable.

Some embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. include thosecomprising Al₂O₃ (in some embodiments preferably, at least 20, 25, 30,35, 40, 45, 50, 55, 60, 65, or even at least 70 percent by weight Al₂O₃,based on the total weight of the glass-ceramic), at least 15 (in someembodiments preferably, at least 20, 25, 30, 35, 40, or even at least45) percent by weight ZrO₂, based on the total weight of the amorphousmaterial or glass-ceramic, as applicable) percent by weight ZrO₂, basedon the total weight of the amorphous material or glass-ceramic, asapplicable, and Y₂O₃ (in some embodiments preferably, at least 0.5 to15%, more preferably 1 to 10 percent by weight Y₂O₃, based on the totalweight of the amorphous material or glass-ceramic, as applicable),wherein at least a portion of the Y₂O₃ forms a distinct crystallinephase during heat-treating.

Some embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. include thosecomprising Al₂O₃ (in some embodiments preferably, at least 20, 25, 30,35, 40, 45, 50, 55, 60, 65, or even at least 70 percent by weight Al₂O₃,based on the total weight of the glass-ceramic), at least 15 (in someembodiments preferably, at least 20, 25, 30, 35, 40, or even at least45) percent by weight ZrO₂, based on the total weight of the amorphousmaterial or glass-ceramic, as applicable) percent by weight ZrO₂, basedon the total weight of the amorphous material or glass-ceramic, asapplicable, and Y₂O₃ (in some embodiments preferably, at least 0.5 to15%, more preferably 1 to 10 percent by weight Y₂O₃, based on the totalweight of the amorphous material or glass-ceramic, as applicable),wherein at least a portion of the Y₂O₃ forms a distinct crystallinephase during heat-treating.

Some embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. include thosecomprising Al₂O₃ (in some embodiments preferably, at least 20, 25, 30,35, 40, 45, 50, 55, 60, 65, or even at least 70 percent by weight Al₂O₃,based on the total weight of the amorphous material or glass-ceramic, asapplicable), at least 15 (in some embodiments preferably, at least 20,25, 30, 35, 40, or even at least 45) percent by weight ZrO₂, based onthe total weight of the amorphous material or glass-ceramic, asapplicable, and contains not more than 10 (in some embodiments,preferably not more than 5, 4, 3, 2, 1, or zero) percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thebased on the total weight of the amorphous material or glass-ceramic, asapplicable, wherein the amorphous material or glass-ceramic, asapplicable, has x, y, and z dimensions each perpendicular to each other,and wherein each of the x, y, and z dimensions is at least 25micrometers (in some embodiments, preferably, at least 30 micrometers,35 micrometers, 40 micrometers, 45 micrometers, 50 micrometers, 75micrometers, 100 micrometers, 150 micrometers, 200 micrometers, 250micrometers, 500 micrometers, 1000 micrometers, 2000 micrometers, 2500micrometers, 1 mm, 5 mm, or even at least 10 mm).

Some embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. include thosecomprising Al₂O₃ (in some embodiments preferably, at least 20, 25, 30,35, 40, 45, 50, 55, 60, 65, or even at least 70 percent by weight Al₂O₃,based on the total weight of the amorphous material or glass-ceramic, asapplicable), ZrO₂ (in some embodiments preferably, at least 20, 25, 30,35, 40, or even at least 45 percent by weight ZrO₂, based on the totalweight of the amorphous material or glass-ceramic, as applicable), and ametal oxide other than Al₂O₃ or ZrO₂ (e.g., Y₂O₃, REO, MgO, TiO₂, NiO,CaO, Cr₂O₃, CuO and complex metal oxides thereof), wherein at least aportion of the metal oxide other than Al₂O₃ or ZrO₂ forms a distinctcrystalline phase during heat-treating, wherein the amorphous materialor glass-ceramic, as applicable, comprises at least 50 percent by weightcollectively of the Al₂O₃ and the ZrO₂, based on the total weight of theamorphous material or glass-ceramic, as applicable, wherein theamorphous material or glass-ceramic, as applicable, contains not morethan 20 (in some embodiments, preferably not more than 15, 10, 5, 4, 3,2, 1, or zero) percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the amorphousmaterial or glass-ceramic, as applicable, wherein the amorphous materialor glass-ceramic, as applicable, has x, y, and z dimensions eachperpendicular to each other, wherein each of the x, y, and z dimensionsis at least 25 micrometers (in some embodiments, preferably, at least 30micrometers, 35 micrometers, 40 micrometers, 45 micrometers, 50micrometers, 75 micrometers, 100 micrometers, 150 micrometers, 200micrometers, 250 micrometers, 500 micrometers, 1000 micrometers, 2000micrometers, 2500 micrometers, 1 mm, 5 mm, or even at least 10 mm).

Optionally, if embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. described hereindo not already specify, embodiments of the amorphous materials,glass-ceramics, etc. may preferably contain not more than 10 (in someembodiments preferably, less than 5, 4, 3, 2, 1, or even zero) percentby weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅,based on the total weight of the ceramics, abrasive particles, etc.described herein do not already specify, embodiments of the amorphousmaterials or glass-ceramic, as applicable.

Optionally, if embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. described hereindo not already specify, embodiments of the amorphous material orglass-ceramic, as applicable, may preferably contain not more than 15,10, 5, 4, 3, 2, 1, or even zero percent by weight SiO₂, based on thetotal weight of the amorphous material or glass-ceramic, as applicable.

Optionally, if embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. described hereindo not already specify, embodiments of the amorphous material orglass-ceramic, as applicable, preferably contain not more than 10, 5, 4,3, 2, 1, or even zero percent by weight B₂O₃ and not more than 10, 5, 4,3, 2, 1, or even zero percent by weight B₂O₃, based on the total weightof the amorphous material or glass-ceramic, as applicable.

Optionally, if embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. described hereindo not already specify, embodiments of the amorphous material orglass-ceramic, as applicable, preferably contain not more than 10, 5, 4,3, 2, 1, or even zero percent by weight collectively SiO₂, B₂O₃, andP₂O₅, based on the total weight of the amorphous material orglass-ceramic, as applicable.

Optionally, if embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. described hereindo not already specify, at least a portion of the amorphous material hasx, y, and z dimensions each perpendicular to each other, and whereineach of the x, y, and z dimensions is at least 10 micrometers, at least25 micrometers, at least 30 micrometers, 35 micrometers, 40 micrometers,45 micrometers, 50 micrometers, 75 micrometers, 100 micrometers, 150micrometers, 200 micrometers, 250 micrometers, 500 micrometers, 1000micrometers, 2000 micrometers, 2500 micrometers, 1 mm, 5 mm, or even atleast 10 mm.

Optionally, if embodiments of amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. described hereincomprise at least 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or even atleast 70 percent by weight Al₂O₃, based on the total weight of theamorphous material or glass-ceramic, as applicable.

In some embodiments, amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. preferablycomprise Al₂O₃ in a range of about 55 to about 65 percent by weight to arange of about 45 to about 35 percent by weight ZrO₂, based on the totalAl₂O₃ and ZrO₂ content of the amorphous material or glass-ceramic, asapplicable. In some embodiments, amorphous materials (includingglasses), glass-ceramics, abrasive particles according to the presentinvention comprising the glass-ceramics, amorphous materials (includingglasses) for making the glass-ceramics, abrasive particles, etc.preferably comprise about 60 percent by weight Al₂O₃ and about 40percent by weight ZrO₂, based on the total Al₂O₃ and ZrO₂ content of theamorphous material or glass-ceramic, as applicable.

In some embodiments, amorphous materials (including glasses),glass-ceramics, abrasive particles according to the present inventioncomprising the glass-ceramics, amorphous materials (including glasses)for making the glass-ceramics, abrasive particles, etc. the weight ratioof Al₂O₃ to ZrO₂ is preferably in a range from 1:10 to 10:1, morepreferably, about 3:2.

Amorphous materials (e.g., glasses), ceramics comprising the amorphousmaterial, particles comprising the amorphous material, etc. can be made,for example, by heating (including in a flame) the appropriate metaloxide sources to form a melt, desirably a homogenous melt, and thenrapidly cooling the melt to provide amorphous material. Embodiments ofamorphous materials can be made, for example, by melting the metal oxidesources in any suitable furnace (e.g., an inductive heated furnace, agas-fired furnace, or an electrical furnace), or, for example, in aplasma. The resulting melt is cooled (e.g., discharging the melt into acooling media (e.g., high velocity air jets, liquids, metal plates(including chilled metal plates), metal rolls (including chilled metalrolls), metal balls (including chilled metal balls), and the like)).

Embodiments of amorphous material can be made utilizing flame fusion asdisclosed, for example, in U.S. Pat. No. 6,254,981 (Castle), thedisclosure of which is incorporated herein by reference. In this method,the metal oxide sources materials are fed (e.g., in the form ofparticles, sometimes referred to as “feed particles”) directly into aburner (e.g., a methane-air burner, an acetylene-oxygen burner, ahydrogen-oxygen burner, and like), and then quenched, for example, inwater, cooling oil, air, or the like. Feed particles can be formed, forexample, by grinding, agglomerating (e.g., spray-drying), melting, orsintering the metal oxide sources. The size of feed particles fed intothe flame generally determine the size of the resulting amorphousmaterial comprising particles.

Embodiments of amorphous materials can also be obtained by othertechniques, such as: laser spin melt with free fall cooling, Taylor wiretechnique, plasmatron technique, hammer and anvil technique, centrifugalquenching, air gun splat cooling, single roller and twin rollerquenching, roller-plate quenching and pendant drop melt extraction (see,e.g., Rapid Solidification of Ceramics, Brockway et. al., Metals AndCeramics Information Center, A Department of Defense InformationAnalysis Center, Columbus, Ohio, January, 1984, the disclosure of whichis incorporated here as a reference). Embodiments of amorphous materialsmay also be obtained by other techniques, such as: thermal (includingflame or laser or plasma-assisted) pyrolysis of suitable precursors,physical vapor synthesis (PVS) of metal precursors and mechanochemicalprocessing.

Useful amorphous material formulations include those at or near aeutectic composition(s) (e.g., binary and ternary eutecticcompositions). In addition to compositions disclosed herein, othercompositions, including quaternary and other higher order eutecticcompositions, may be apparent to those skilled in the art afterreviewing the present disclosure.

Sources, including commercial sources, of (on a theoretical oxide basis)Al₂O₃ include bauxite (including both natural occurring bauxite andsynthetically produced bauxite), calcined bauxite, hydrated aluminas(e.g., boehmite, and gibbsite), aluminum, Bayer process alumina,aluminum ore, gamma alumina, alpha alumina, aluminum salts, aluminumnitrates, and combinations thereof. The Al₂O₃ source may contain, oronly provide, Al₂O₃. Alternatively, the Al₂O₃ source may contain, orprovide Al₂O₃, as well as one or more metal oxides other than Al₂O₃(including materials of or containing complex Al₂O₃.metal oxides (e.g.,Dy₃Al₅O₁₂, Y₃Al₅O₁₂, CeAl₁₁O₁₈, etc.)).

Sources, including commercial sources, of (on a theoretical oxide basis)ZrO₂ include zirconium oxide powders, zircon sand, zirconium,zirconium-containing ores, and zirconium salts (e.g., zirconiumcarbonates, acetates, nitrates, chlorides, hydroxides, and combinationsthereof). In addition, or alternatively, the ZrO₂ source may contain, orprovide ZrO₂, as well as other metal oxides such as hafnia. Sources,including commercial sources, of (on a theoretical oxide basis) HfO₂include hafnium oxide powders, hafnium, hafnium-containing ores, andhafnium salts. In addition, or alternatively, the HfO₂ source maycontain, or provide HfO₂, as well as other metal oxides such as ZrO₂. Itmay be desirable to add metal oxides (e.g., Y₂O₃, TiO₂, CaO, and MgO)that are known to stabilize tetragonal/cubic form of ZrO₂.

Sources, including commercial sources, of rare earth oxides include rareearth oxide powders, rare earth metals, rare earth-containing ores(e.g., bastnasite and monazite), rare earth salts, rare earth nitrates,and rare earth carbonates. The rare earth oxide(s) source may contain,or only provide, rare earth oxide(s). Alternatively, the rare earthoxide(s) source may contain, or provide rare earth oxide(s), as well asone or more metal oxides other than rare earth oxide(s) (includingmaterials of or containing complex rare earth oxide.other metal oxides(e.g., Dy₃Al₅O₁₂, CeAl₁₁O₁₈, etc.)).

Sources, including commercial sources, of (on a theoretical oxide basis)Y₂O₃ include yttrium oxide powders, yttrium, yttrium-containing ores,and yttrium salts (e.g., yttrium carbonates, nitrates, chlorides,hydroxides, and combinations thereof). The Y₂O₃ source may contain, oronly provide, Y₂O₃. Alternatively, the Y₂O₃ source may contain, orprovide Y₂O₃, as well as one or more metal oxides other than Y₂O₃(including materials of or containing complex Y₂O₃.metal oxides (e.g.,Y₃Al₅O₁₂)).

Other useful metal oxide may also include, on a theoretical oxide basis,BaO, CaO, Cr₂O₃, CoO, Fe₂O₃, GeO₂, Li₂O, MgO, MnO, NiO, Na₂O, Sc₂O₃,SrO, TiO₂, ZnO, and combinations thereof. Sources, including commercialsources, include the oxides themselves, complex oxides, ores,carbonates, acetates, nitrates, chlorides, hydroxides, etc. These metaloxides are added to modify a physical property of the resulting abrasiveparticles and/or improve processing. These metal oxides are typicallyare added anywhere from 0 to 50% by weight, in some embodimentspreferably 0 to 25% by weight and more preferably 0 to 50% by weight ofthe glass-ceramic depending, for example, upon the desired property.

In some embodiments, it may be advantageous for at least a portion of ametal oxide source (in some embodiments, preferably, 10 15, 20, 25, 30,35, 40, 45, or even at least 50 percent by weight) to be obtained byadding particulate, metallic material comprising at least one of a metal(e.g., Al, Ca, Cu, Cr, Fe, Li, Mg, Ni, Ag, Ti, Zr, and combinationsthereof), M, that has a negative enthalpy of oxide formation or an alloythereof to the melt, or otherwise metal them with the other rawmaterials. Although not wanting to be bound by theory, it is believedthat the heat resulting from the exothermic reaction associated with theoxidation of the metal is beneficial in the formation of a homogeneousmelt and resulting amorphous material. For example, it is believed thatthe additional heat generated by the oxidation reaction within the rawmaterial eliminates or minimizes insufficient heat transfer, and hencefacilitates formation and homogeneity of the melt, particularly whenforming amorphous particles with x, y, and z dimensions over 150micrometers. It is also believed that the availability of the additionalheat aids in driving various chemical reactions and physical processes(e.g., densification, and spherodization) to completion. Further, it isbelieved for some embodiments, the presence of the additional heatgenerated by the oxidation reaction actually enables the formation of amelt, which otherwise is difficult or otherwise not practical due tohigh melting point of the materials. Further, the presence of theadditional heat generated by the oxidation reaction actually enables theformation of amorphous material that otherwise could not be made, orcould not be made in the desired size range. Another advantage of theinvention include, in forming the amorphous materials, that many of thechemical and physical processes such as melting, densification andspherodizing can be achieved in a short time, so that very high quenchrates be can achieved. For additional details, see copending applicationhaving U.S. Ser. No. 10/211,639, filed the same date as the instantapplication, the disclosure of which is incorporated herein byreference.

The particular selection of metal oxide sources and other additives formaking ceramics according to the present invention typically takes intoaccount, for example, the desired composition and microstructure of theresulting ceramics, the desired degree of crystallinity, if any, thedesired physical properties (e.g., hardness or toughness) of theresulting ceramics, avoiding or minimizing the presence of undesirableimpurities, the desired characteristics of the resulting ceramics,and/or the particular process (including equipment and any purificationof the raw materials before and/or during fusion and/or solidification)being used to prepare the ceramics.

The addition of certain metal oxides may alter the properties and/orcrystalline structure or microstructure of a glass-ceramic according tothe present invention, as well as the processing of the raw materialsand intermediates in making the glass-ceramic. For example, oxideadditions such as MgO, CaO, Li₂O, and Na₂O have been observed to alterboth the T_(g) (for a glass) and T_(x) (wherein T_(x) is thecrystallization temperature) of amorphous material. Although not wishingto be bound by theory, it is believed that such additions influenceglass formation. Further, for example, such oxide additions may decreasethe melting temperature of the overall system (i.e., drive the systemtoward lower melting eutectic), and ease of amorphousmaterial-formation. Complex eutectics in multi component systems(quaternary, etc.) may result in better amorphous material-formingability. The viscosity of the liquid melt and viscosity of the glass inits “working” range may also be affected by the addition of certainmetal oxides such as MgO, CaO, Li₂O, and Na₂O. It is also within thescope of the present invention to incorporate at least one of halogens(e.g., fluorine and chlorine), or chalcogenides (e.g., sulfides,selenides, and tellurides) into the amorphous materials, and theglass-ceramics made there from.

Crystallization of the amorphous material and ceramic comprising theamorphous material may also be affected by the additions of certainmaterials. For example, certain metals, metal oxides (e.g., titanatesand zirconates), and fluorides, for example, may act as nucleationagents resulting in beneficial heterogeneous nucleation of crystals.Also, addition of some oxides may change nature of metastable phasesdevitrifying from the amorphous material upon reheating.

The particular selection of metal oxide sources and other additives formaking ceramics according to the present invention typically takes intoaccount, for example, the desired composition and microstructure of theresulting ceramics, the desired degree of crystallinity, if any, thedesired physical properties (e.g., hardness or toughness) of theresulting ceramics, avoiding or minimizing the presence of undesirableimpurities, the desired characteristics of the resulting ceramics,and/or the particular process (including equipment and any purificationof the raw materials before and/or during fusion and/or solidification)being used to prepare the ceramics.

The metal oxide sources and other additives can be in any form suitableto the process and equipment being used to make the amorphous materialsaccording to the present invention, the glass-ceramics according to thepresent invention, etc. The raw materials can be melted and quenchedusing techniques and equipment known in the art for making oxideamorphous materials and amorphous metals. Desirable cooling ratesinclude those of 50 K/s and greater. Cooling techniques known in the artinclude roll-chilling. Roll-chilling can be carried out, for example, bymelting the metal oxide sources at a temperature typically 20–200° C.higher than the melting point, and cooling/quenching the melt byspraying it under high pressure (e.g., using a gas such as air, argon,nitrogen or the like) onto a high-speed rotary roll(s). Typically, therolls are made of metal and are water cooled. Metal book molds may alsobe useful for cooling/quenching the melt.

Other techniques for forming melts, cooling/quenching melts, and/orotherwise forming amorphous material include vapor phase quenching,melt-extraction, plasma spraying, and gas or centrifugal atomization.Vapor phase quenching can be carried out, for example, by sputtering,wherein the metal alloys or metal oxide sources are formed into asputtering target(s) which are used. The target is fixed at apredetermined position in a sputtering apparatus, and a substrate(s) tobe coated is placed at a position opposing the target(s). Typicalpressures of 10⁻³ torr of oxygen gas and Ar gas, discharge is generatedbetween the target(s) and a substrate(s), and Ar or oxygen ions collideagainst the target to start reaction sputtering, thereby depositing afilm of composition on the substrate. For additional details regardingplasma spraying, see, for example, copending application having U.S.Ser. No. 10/211,640, filed the same date as the instant application, thedisclosure of which is incorporated herein by reference.

Gas atomization involves melting feed particles to convert them to melt.A thin stream of such melt is atomized through contact with a disruptiveair jet (i.e., the stream is divided into fine droplets). The resultingsubstantially discrete, generally ellipsoidal amorphous materialcomprising particles (e.g., beads) are then recovered. Examples of beadsizes include those having a diameter in a range of about 5 micrometersto about 3 mm. Melt-extraction can be carried out, for example, asdisclosed in U.S. Pat. No. 5,605,870 (Strom-Olsen et al.), thedisclosure of which is incorporated herein by reference. Containerlessglass forming techniques utilizing laser beam heating as disclosed, forexample, in PCT application having Publication No. WO 01/27046 A1,published Apr. 4, 2001, the disclosure of which is incorporated hereinby reference, may also be useful in making materials according to thepresent invention.

The cooling rate is believed to affect the properties of the quenchedamorphous material. For instance, glass transition temperature, densityand other properties of glass typically change with cooling rates.

Typically, it is preferred that the bulk material comprises at least 50,60, 75, 80, 85, 90, 95, 98, 99, or even 100 percent by weight of theamorphous material.

Rapid cooling may also be conducted under controlled atmospheres, suchas a reducing, neutral, or oxidizing environment to maintain and/orinfluence the desired oxidation states, etc. during cooling. Theatmosphere can also influence amorphous material formation byinfluencing crystallization kinetics from undercooled liquid. Forexample, larger undercooling of Al₂O₃ melts without crystallization hasbeen reported in argon atmosphere as compared to that in air.

The microstructure or phase composition (glassy/amorphous/crystalline)of a material can be determined in a number of ways. Various informationcan be obtained using optical microscopy, electron microscopy,differential thermal analysis (DTA), and x-ray diffraction (XRD), forexample.

Using optical microscopy, amorphous material is typically predominantlytransparent due to the lack of light scattering centers such as crystalboundaries, while crystalline material shows a crystalline structure andis opaque due to light scattering effects.

A percent amorphous yield can be calculated for beads using a −100+120mesh size fraction (i.e., the fraction collected between 150-micrometeropening size and 125-micrometer opening size screens). The measurementsare done in the following manner. A single layer of beads is spread outupon a glass slide. The beads are observed using an optical microscope.Using the crosshairs in the optical microscope eyepiece as a guide,beads that lay along a straight line are counted either amorphous orcrystalline depending on their optical clarity. A total of 500 beads arecounted and a percent amorphous yield is determined by the amount ofamorphous beads divided by total beads counted.

Using DTA, the material is classified as amorphous if the correspondingDTA trace of the material contains an exothermic crystallization event(T_(x)). If the same trace also contains an endothermic event (T_(g)) ata temperature lower than T_(x) it is considered to consist of a glassphase. If the DTA trace of the material contains no such events, it isconsidered to contain crystalline phases.

Differential thermal analysis (DTA) can be conducted using the followingmethod. DTA runs can be made (using an instrument such as that obtainedfrom Netzsch Instruments, Selb, Germany under the trade designation“NETZSCH STA 409 DTA/TGA”) using a −140+170 mesh size fraction (i.e.,the fraction collected between 105-micrometer opening size and90-micrometer opening size screens). An amount of each screened sample(typically about 400 milligrams (mg)) is placed in a 100-microliterAl₂O₃ sample holder. Each sample is heated in static air at a rate of10° C./minute from room temperature (about 25° C.) to 1100° C.

Using powder x-ray diffraction, XRD, (using an x-ray diffractometer suchas that obtained under the trade designation “PHILLIPS XRG 3100” fromPhillips, Mahwah, N.J., with copper K α1 radiation of 1.54050 Angstrom)the phases present in a material can be determined by comparing thepeaks present in the XRD trace of the crystallized material to XRDpatterns of crystalline phases provided in JCPDS (Joint Committee onPowder Diffraction Standards) databases, published by InternationalCenter for Diffraction Data. Furthermore, an XRD can be usedqualitatively to determine types of phases. The presence of a broaddiffused intensity peak is taken as an indication of the amorphousnature of a material. The existence of both a broad peak andwell-defined peaks is taken as an indication of existence of crystallinematter within an amorphous matrix.

The initially formed amorphous material or ceramic (including glassprior to crystallization) may be larger in size than that desired. Theamorphous material or ceramic can be converted into smaller pieces usingcrushing and/or comminuting techniques known in the art, including rollcrushing, canary milling, jaw crushing, hammer milling, ball milling,jet milling, impact crushing, and the like. In some instances, it isdesired to have two or multiple crushing steps. For example, after theceramic is formed (solidified), it may be in the form of larger thandesired. The first crushing step may involve crushing these relativelylarge masses or “chunks” to form smaller pieces. This crushing of thesechunks may be accomplished with a hammer mill, impact crusher or jawcrusher. These smaller pieces may then be subsequently crushed toproduce the desired particle size distribution. In order to produce thedesired particle size distribution (sometimes referred to as grit sizeor grade), it may be necessary to perform multiple crushing steps. Ingeneral the crushing conditions are optimized to achieve the desiredparticle shape(s) and particle size distribution. Resulting particlesthat are of the desired size may be recrushed if they are too large, or“recycled” and used as a raw material for re-melting if they are toosmall.

The shape of the ceramic (including glass prior to crystallization) maydepend, for example, on the composition and/or microstructure of theceramic, the geometry in which it was cooled, and the manner in whichthe ceramic is crushed (i.e., the crushing technique used). In general,where a “blocky” shape is preferred, more energy may be employed toachieve this shape. Conversely, where a “sharp” shape is preferred, lessenergy may be employed to achieve this shape. The crushing technique mayalso be changed to achieve different desired shapes. The resultingparticle may have an average aspect ratio ranging from 1:1 to 5:1,typically 1.25:1 to 3:1 and preferably 1.5:1 to 2.5:1.

It is also within the scope of the present invention, for example, todirectly form ceramic (including glass prior to crystallization) may indesired shapes. For example, ceramic (including glass prior tocrystallization) may be formed (including molded) by pouring or formingthe melt into a mold.

It is also within the scope of the present invention, for example, tofabricate the ceramic (including glass prior to crystallization) bycoalescing. This coalescing step in essence forms a larger sized bodyfrom two or more smaller particles. For example, amorphous materialcomprising particles (obtained, for example, by crushing) (includingbeads and microspheres), fibers, etc. may formed into a larger particlesize. For example, ceramic (including glass prior to crystallization),may also be provided by heating, for example, particles comprising theamorphous material, and/or fibers, etc. above the T_(g) such that theparticles, etc. coalesce to form a shape and cooling the coalescedshape. The temperature and pressure used for coalescing may depend, forexample, upon composition of the amorphous material and the desireddensity of the resulting material. The temperature should below glasscrystallization temperature, and for glasses, greater than the glasstransition temperature. In certain embodiments, the heating is conductedat at least one temperature in a range of about 850° C. to about 1100°C. (in some embodiments, preferably 900° C. to 1000° C.). Typically, theamorphous material is under pressure (e.g., greater than zero to 1 GPaor more) during coalescence to aid the coalescence of the amorphousmaterial. In one embodiment, a charge of the particles, etc. is placedinto a die and hot-pressing is performed at temperatures above glasstransition where viscous flow of glass leads to coalescence into arelatively large part. Examples of typical coalescing techniques includehot pressing, hot isostatic pressure, hot extrusion and the like.Typically, it is generally preferred to cool the resulting coalescedbody before further heat treatment. After heat treatment if so desired,the coalesced body may be crushed to smaller particle sizes or a desiredparticle size distribution.

It is also within the scope of the present invention to conductadditional heat-treatment to further improve desirable properties of thematerial. For example, hot-isostatic pressing may be conducted (e.g., attemperatures from about 900° C. to about 1400° C.) to remove residualporosity, increasing the density of the material. Optionally, theresulting, coalesced article can be heat-treated to provideglass-ceramic, crystalline ceramic, or ceramic otherwise comprisingcrystalline ceramic.

Coalescence of the amorphous material and/or glass-ceramic (e.g.,particles) may also be accomplished by a variety of methods, includingpressureless or pressure sintering (e.g., sintering, plasma assistedsintering, hot pressing, HIPing, hot forging, hot extrusion, etc.).

Heat-treatment can be carried out in any of a variety of ways, includingthose known in the art for heat-treating glass to provideglass-ceramics. For example, heat-treatment can be conducted in batches,for example, using resistive, inductively or gas heated furnaces.Alternatively, for example, heat-treatment can be conductedcontinuously, for example, using rotary kilns. In the case of a rotarykiln, the material is fed directly into a kiln operating at the elevatedtemperature. The time at the elevated temperature may range from a fewseconds (in some embodiments even less than 5 seconds) to a few minutesto several hours. The temperature may range anywhere from 900° C. to1600° C., typically between 1200° C. to 1500° C. It is also within thescope of the present invention to perform some of the heat-treatment inbatches (e.g., for the nucleation step) and another continuously (e.g.,for the crystal growth step and to achieve the desired density). For thenucleation step, the temperature typically ranges between about 900° C.to about 1100° C., in some embodiments, preferably in a range from about925° C. to about 1050° C. Likewise for the density step, the temperaturetypically is in a range from about 1100° C. to about 1600° C., in someembodiments, preferably in a range from about 1200° C. to about 1500° C.This heat treatment may occur, for example, by feeding the materialdirectly into a furnace at the elevated temperature. Alternatively, forexample, the material may be feed into a furnace at a much lowertemperature (e.g., room temperature) and then heated to desiredtemperature at a predetermined heating rate. It is within the scope ofthe present invention to conduct heat-treatment in an atmosphere otherthan air. In some cases it might be even desirable to heat-treat in areducing atmosphere(s). Also, for, example, it may be desirable toheat-treat under gas pressure as in, for example, hot-isostatic press,or in gas pressure furnace. It is within the scope of the presentinvention to convert (e.g., crush) the resulting article or heat-treatedarticle to provide particles (e.g., abrasive particles).

The amorphous material is heat-treated to at least partially crystallizethe amorphous material to provide glass-ceramic. The heat-treatment ofcertain glasses to form glass-ceramics is well known in the art. Theheating conditions to nucleate and grow glass-ceramics are known for avariety of glasses. Alternatively, one skilled in the art can determinethe appropriate conditions from a Time-Temperature-Transformation (TTT)study of the glass using techniques known in the art. One skilled in theart, after reading the disclosure of the present invention should beable to provide TTT curves for glasses according to the presentinvention, determine the appropriate nucleation and/or crystal growthconditions to provide glass-ceramics according to the present invention.

Typically, glass-ceramics are stronger than the amorphous materials fromwhich they are formed. Hence, the strength of the material may beadjusted, for example, by the degree to which the amorphous material isconverted to crystalline ceramic phase(s). Alternatively, or inaddition, the strength of the material may also be affected, forexample, by the number of nucleation sites created, which may in turn beused to affect the number, and in turn the size of the crystals of thecrystalline phase(s). For additional details regarding formingglass-ceramics, see, for example, Glass-Ceramics, P. W. McMillan,Academic Press, Inc., 2^(nd) edition, 1979, the disclosure of which isincorporated herein by reference.

For example, during heat-treatment of some exemplary amorphous materialsfor making glass-ceramics according to present invention, formation ofphases such as La₂Zr₂O₇, and, if ZrO₂ is present, cubic/tetragonal ZrO₂,in some cases monoclinic ZrO₂, have been observed at temperatures aboveabout 900° C. Although not wanting to be bound by theory, it is believedthat zirconia-related phases are the first phases to nucleate from theamorphous material. Formation of Al₂O₃, ReAlO₃ (wherein Re is at leastone rare earth cation), ReAl₁₁O₁₈, Re₃Al₅O₁₂, Y₃Al₅O₁₂, etc. phases arebelieved to generally occur at temperatures above about 925° C.Typically, crystallite size during this nucleation step is on order ofnanometers. For example, crystals as small as 10–15 nanometers have beenobserved. For at least some embodiments, heat-treatment at about 1300°C. for about 1 hour provides a full crystallization. In generally,heat-treatment times for each of the nucleation and crystal growth stepsmay range of a few seconds (in some embodiments even less than 5seconds) to several minutes to an hour or more.

The size of the resulting crystals can typically controlled at least inpart by the nucleation and/or crystallization times and/or temperatures.Although it is generally preferred to have small crystals (e.g., on theorder not greater than a micrometer, or even not greater than ananometer) glass-ceramics according to the present invention may be madewith larger crystal sizes (e.g., at least 1–10 micrometers, at least10–25 micrometers, at least 50–100 micrometers, or even grater than 100micrometers). Although not wanting to be bound by theory, it isgenerally believed in the art that the finer the size of the crystals(for the same density), the higher the mechanical properties (e.g.,hardness and strength) of the ceramic.

Examples of crystalline phases which may be present in embodiments ofglass-ceramics according to the present invention include: Al₂O₃ (e.g.,α-Al₂O₃), Y₂O₃, REO, HfO₂ ZrO₂ (e.g., cubic ZrO₂ and tetragonal ZrO₂),BaO, CaO, Cr₂O₃, CoO, Fe₂O₃, GeO₂, Li₂O, MgO, MnO, NiO, Na₂O, P₂O₅,Sc₂O₃, SiO₂, SrO, TeO₂, TiO₂, V₂O₃, Y₂O₃, ZnO, “complex metal oxides”(including “complex Al₂O₃.metal oxide (e.g., complex Al₂O₃.REO (e.g.,ReAlO₃ (e.g., GdAlO₃ LaAlO₃), ReAl₁₁O₁₈ (e.g., LaAl₁₁O₁₈,), andRe₃Al₅O₁₂ (e.g., Dy₃Al₅O₁₂)), complex Al₂O₃.Y₂O₃ (e,g., Y₃Al₅O₁₂), andcomplex ZrO₂.REO (e.g., Re₂Zr₂O₇ (e.g., La₂Zr₂O₇))), and combinationsthereof.

It is also with in the scope of the present invention to substitute aportion of the yttrium and/or aluminum cations in a complex Al₂O₃.metaloxide (e.g., complex Al₂O₃.Y₂O₃ (e.g., yttrium aluminate exhibiting agarnet crystal structure)) with other cations. For example, a portion ofthe Al cations in a complex Al₂O₃.Y₂O₃ may be substituted with at leastone cation of an element selected from the group consisting of: Cr, Ti,Sc, Fe, Mg, Ca, Si, Co, and combinations thereof. For example, a portionof the Y cations in a complex Al₂O₃.Y₂O₃ may be substituted with atleast one cation of an element selected from the group consisting of:Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Th, Tm, Yb, Fe, Ti, Mn, V,Cr, Co, Ni, Cu, Mg, Ca, Sr, and combinations thereof. Similarly, it isalso with in the scope of the present invention to substitute a portionof the aluminum cations in alumina. For example, Cr, Ti, Sc, Fe, Mg, Ca,Si, and Co can substitute for aluminum in the alumina. The substitutionof cations as described above may affect the properties (e.g. hardness,toughness, strength, thermal conductivity, etc.) of the fused material.

It is also with in the scope of the present invention to substitute aportion of the rare earth and/or aluminum cations in a complexAl₂O₃.metal oxide (e.g., complex Al₂O₃.REO) with other cations. Forexample, a portion of the Al cations in a complex Al₂O₃.REO may besubstituted with at least one cation of an element selected from thegroup consisting of: Cr, Ti, Sc, Fe, Mg, Ca, Si, Co, and combinationsthereof. For example, a portion of the Y cations in a complex Al₂O₃.REOmay be substituted with at least one cation of an element selected fromthe group consisting of: Y, Fe, Ti, Mn, V, Cr, Co, Ni, Cu, Mg, Ca, Sr,and combinations thereof. Similarly, it is also with in the scope of thepresent invention to substitute a portion of the aluminum cations inalumina. For example, Cr, Ti, Sc, Fe, Mg, Ca, Si, and Co can substitutefor aluminum in the alumina. The substitution of cations as describedabove may affect the properties (e.g. hardness, toughness, strength,thermal conductivity, etc.) of the fused material.

The average crystal size can be determined by the line intercept methodaccording to the ASTM standard E 112-96 “Standard Test Methods forDetermining Average Grain Size”. The sample is mounted in mounting resin(such as that obtained under the trade designation “TRANSOPTIC POWDER”from Buehler, Lake Bluff, Ill.) typically in a cylinder of resin about2.5 cm in diameter and about 1.9 cm high. The mounted section isprepared using conventional polishing techniques using a polisher (suchas that obtained from Buehler, Lake Bluff, Ill. under the tradedesignation “ECOMET 3”). The sample is polished for about 3 minutes witha diamond wheel, followed by 5 minutes of polishing with each of 45, 30,15, 9, 3, and 1-micrometer slurries. The mounted and polished sample issputtered with a thin layer of gold-palladium and viewed using ascanning electron microscopy (such as the JEOL SEM Model JSM 840A). Atypical back-scattered electron (BSE) micrograph of the microstructurefound in the sample is used to determine the average crystal size asfollows. The number of crystals that intersect per unit length (N_(L))of a random straight line drawn across the micrograph are counted. Theaverage crystal size is determined from this number using the followingequation.

${{Average}\mspace{14mu}{Crystal}\mspace{14mu}{Size}} = \frac{1.5}{N_{L}M}$

Where N_(L) is the number of crystals intersected per unit length and Mis the magnification of the micrograph.

Some embodiments of the present invention include glass-ceramicscomprising alpha alumina having at least one of an average crystal sizenot greater than 150 nanometers.

Some embodiments of the present invention include glass-ceramicscomprising alpha alumina, wherein at least 90 (in some embodimentspreferably, 95, or even 100) percent by number of the alpha aluminapresent in such portion have crystal sizes not greater than 200nanometers.

Some embodiments of the present invention include glass-ceramicscomprising alpha Al₂O₃, crystalline ZrO₂, and a first complexAl₂O₃.Y₂O₃, and wherein at least one of the alpha Al₂O₃, the crystallineZrO₂, or the first complex Al₂O₃.Y₂O₃ has an average crystal size notgreater than 150 nanometers. In some embodiments preferably, theglass-ceramics further comprise a second, different complex Al₂O₃.Y₂O₃.In some embodiments preferably, the glass-ceramics further comprise acomplex Al₂O₃.REO.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.Y₂O₃, a second, different complexAl₂O₃.Y₂O₃, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃.Y₂O₃, the second complex Al₂O₃.Y₂O₃, or thecrystalline ZrO₂, at least 90 (in some embodiments preferably, 95, oreven 100) percent by number of the crystal sizes thereof are not greaterthan 200 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a second, different complex Al₂O₃.Y₂O₃. In someembodiments preferably, the glass-ceramics further comprise a complexAl₂O₃.REO.

Some embodiments of the present invention include glass-ceramicscomprising alpha Al₂O₃, crystalline ZrO₂, and a first complex Al₂O₃.REO,and wherein at least one of the alpha Al₂O₃, the crystalline ZrO₂, orthe first complex Al₂O₃.REO has an average crystal size not greater than150 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a second, different complex Al₂O₃.REO. In someembodiments preferably, the glass-ceramics further comprise a complexAl₂O₃.Y₂O₃.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.REO, a second, different complexAl₂O₃.REO, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃.REO, the second complex Al₂O₃.REO, or thecrystalline ZrO₂, at least 90 (in some embodiments preferably, 95, oreven 100) percent by number of the crystal sizes thereof are not greaterthan 200 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a complex Al₂O₃.Y₂O₃.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.Y₂O₃, a second, different complexAl₂O₃.Y₂O₃, and crystalline ZrO₂, and wherein at least one of the firstcomplex Al₂O₃.Y₂O₃, the second, different complex Al₂O₃.Y₂O₃, or thecrystalline ZrO₂ has an average crystal size not greater than 150nanometers. In some embodiments preferably, the glass-ceramics furthercomprise a second, different complex Al₂O₃.Y₂O₃. In some embodimentspreferably, the glass-ceramics further comprise a complex Al₂O₃.REO.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.Y₂O₃, a second, different complexAl₂O₃.Y₂O₃, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃.Y₂O₃, the second, different complex Al₂O₃.Y₂O₃, orthe crystalline ZrO₂, at least 90 (in some embodiments preferably, 95,or even 100) percent by number of the crystal sizes thereof are notgreater than 200 nanometers. In some embodiments preferably, theglass-ceramics further comprise a complex Al₂O₃.REO.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.REO, a second, different complexAl₂O₃.REO, and crystalline ZrO₂, and wherein at least one of the firstcomplex Al₂O₃.REO, the second, different complex Al₂O₃.REO, or thecrystalline ZrO₂ has an average crystal size not greater than 150nanometers. In some embodiments preferably, the glass-ceramics furthercomprise a second, different complex Al₂O₃.REO. In some embodimentspreferably, the glass-ceramics further comprise a complex Al₂O₃.Y₂O₃.

Some embodiments of the present invention include glass-ceramicscomprising a first complex Al₂O₃.REO, a second, different complexAl₂O₃.REO, and crystalline ZrO₂, and wherein for at least one of thefirst complex Al₂O₃.REO, the second, different complex Al₂O₃.REO, or thecrystalline ZrO₂, at least 90 (in some embodiments preferably, 95, oreven 100) percent by number of the crystal sizes thereof are not greaterthan 200 nanometers. In some embodiments preferably, the glass-ceramicsfurther comprise a complex Al₂O₃.Y₂O₃.

In some embodiments, glass-ceramics according to the present inventioncomprise at least 75, 80, 85, 90, 95, 97, 98, 99, or even 100 percent byvolume crystallites, wherein the crystallites have an average size ofless than 1 micrometer. In some embodiments, glass-ceramics according tothe present invention comprise not greater than at least 75, 80, 85, 90,95, 97, 98, 99, or even 100 percent by volume crystallites, wherein thecrystallites have an average size not greater than 0.5 micrometer. Insome embodiments, glass-ceramics according to the present inventioncomprise less than at 75, 80, 85, 90, 95, 97, 98, 99, or even 100percent by volume crystallites, wherein the crystallites have an averagesize not greater than 0.3 micrometer. In some embodiments,glass-ceramics according to the present invention comprise less than atleast 75, 80, 85, 90, 95, 97, 98, 99, or even 100 percent by volumecrystallites, wherein the crystallites have an average size not greaterthan 0.15 micrometer.

Crystals formed by heat-treating amorphous to provide embodiments ofglass-ceramics according to the present invention may be, for example,equiaxed, columnar, or flattened splat-like features.

Although an amorphous material, glass-ceramic, etc. according to thepresent invention may be in the form of a bulk material, it is alsowithin the scope of the present invention to provide compositescomprising an amorphous material, glass-ceramic, etc. according to thepresent invention. Such a composite may comprise, for example, a phaseor fibers (continuous or discontinuous) or particles (includingwhiskers) (e.g., metal oxide particles, boride particles, carbideparticles, nitride particles, diamond particles, metallic particles,glass particles, and combinations thereof) dispersed in an amorphousmaterial, glass-ceramic, etc. according to the present invention,invention or a layered-composite structure (e.g., a gradient ofglass-ceramic to amorphous material used to make the glass-ceramicand/or layers of different compositions of glass-ceramics).

Typically, the (true) density, sometimes referred to as specificgravity, of ceramics according to the present invention is typically atleast 70% of theoretical density. More desirably, the (true) density ofceramic according to the present invention is at least 75%, 80%, 85%,90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.5% or even 100% of theoreticaldensity. Abrasive particles according to the present invention havedensities of at least 85%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 99.5% oreven 100% of theoretical density.

The average hardness of the material of the present invention can bedetermined as follows. Sections of the material are mounted in mountingresin (obtained under the trade designation “TRANSOPTIC POWDER” fromBuehler, Lake Bluff, Ill.) typically in a cylinder of resin about 2.5 cmin diameter and about 1.9 cm high. The mounted section is prepared usingconventional polishing techniques using a polisher (such as thatobtained from Buehler, Lake Bluff, Ill. under the trade designation“ECOMET 3”). The sample is polished for about 3 minutes with a diamondwheel, followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,and 1-micrometer slurries. The microhardness measurements are made usinga conventional microhardness tester (such as that obtained under thetrade designation “MITUTOYO MVK-VL” from Mitutoyo Corporation, Tokyo,Japan) fitted with a Vickers indenter using a 100-gram indent load. Themicrohardness measurements are made according to the guidelines statedin ASTM Test Method E384 Test Methods for Microhardness of Materials(1991), the disclosure of which is incorporated herein by reference.

In some embodiments, glass-ceramic according to the present inventionhave an average hardness of at least 13 GPa (in some embodimentspreferably, at least 14, 15, 16, 17, or even at least 18 GPa). Abrasiveparticles according to the present invention have an average hardness ofat least 15 GPa, in some embodiments, at least 16 GPa, at least 17 GPa,or even at least 18 GPa.

Additional details regarding amorphous materials and glass-ceramics,including making, using, and properties thereof, can be found inapplication having U.S. Ser. Nos. 09/922,526, 09/922,527, and09/922,530, filed Aug. 2, 2001, and U.S. Ser. Nos. 10/211,598,10/211,630, 10/211,639, 10/211,034, 10,211,044, 10/211,640, and10/211,684, filed the same date as the instant application, thedisclosures of which are incorporated herein by reference.

Abrasive particles according to the present invention generally comprisecrystalline ceramic (in some embodiments, preferably at least 75, 80,85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, or even 100 percent byvolume) crystalline ceramic.

Abrasive particles according to the present invention can be screenedand graded using techniques well known in the art, including the use ofindustry recognized grading standards such as ANSI (American NationalStandard Institute), FEPA (Federation Europeenne des Fabricants deProducts Abrasifs), and JIS (Japanese Industrial Standard). Abrasiveparticles according to the present invention may be used in a wide rangeof particle sizes, typically ranging in size from about 0.1 to about5000 micrometers, more typically from about 1 to about 2000 micrometers;desirably from about 5 to about 1500 micrometers, more desirably fromabout 100 to about 1500 micrometers.

ANSI grade designations include: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI24, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120,ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360,ANSI 400, and ANSI 600. Preferred ANSI grades comprising abrasiveparticles according to the present invention are ANSI 8-220. FEPA gradedesignations include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100,P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200.Preferred FEPA grades comprising abrasive particles according to thepresent invention are P12–P220. JIS grade designations include JIS8,JIS12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80, JIS10, JIS150,JIS180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS600, JIS800,JIS1000, JIS1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS10,000.Preferred JIS grades comprising abrasive particles according to thepresent invention are JIS8–220.

After crushing and screening, there will typically be a multitude ofdifferent abrasive particle size distributions or grades. Thesemultitudes of grades may not match a manufacturer's or supplier's needsat that particular time. To minimize inventory, it is possible torecycle the off demand grades back into melt to form amorphous material.This recycling may occur after the crushing step, where the particlesare in large chunks or smaller pieces (sometimes referred to as “fines”)that have not been screened to a particular distribution.

In another aspect, the present invention provides a method for makingabrasive particles, the method comprising heat-treating amorphous (e.g.,glass) comprising particles such that at least a portion of theamorphous material converts to a glass-ceramic to provide abrasiveparticles comprising the glass-ceramic. The present invention alsoprovides a method for making abrasive particles comprising aglass-ceramic, the method comprising heat-treating amorphous materialsuch that at least a portion of the amorphous material converts to aglass-ceramic, and crushing the resulting heat-treated material toprovide the abrasive particles. When crushed, glass tends to providesharper particles than crushing significantly crystallizedglass-ceramics or crystalline material.

In another aspect, the present invention provides agglomerate abrasivegrains each comprise a plurality of abrasive particles according to thepresent invention bonded together via a binder. In another aspect, thepresent invention provides an abrasive article (e.g., coated abrasivearticles, bonded abrasive articles (including vitrified, resinoid, andmetal bonded grinding wheels, cutoff wheels, mounted points, and honingstones), nonwoven abrasive articles, and abrasive brushes) comprising abinder and a plurality of abrasive particles, wherein at least a portionof the abrasive particles are abrasive particles (including where theabrasive particles are agglomerated) according to the present invention.Methods of making such abrasive articles and using abrasive articles arewell known to those skilled in the art. Furthermore, abrasive particlesaccording to the present invention can be used in abrasive applicationsthat utilize abrasive particles, such as slurries of abrading compounds(e.g., polishing compounds), milling media, shot blast media, vibratorymill media, and the like.

Coated abrasive articles generally include a backing, abrasiveparticles, and at least one binder to hold the abrasive particles ontothe backing. The backing can be any suitable material, including cloth,polymeric film, fibre, nonwoven webs, paper, combinations thereof, andtreated versions thereof. The binder can be any suitable binder,including an inorganic or organic binder (including thermally curableresins and radiation curable resins). The abrasive particles can bepresent in one layer or in two layers of the coated abrasive article.

An example of a coated abrasive article according to the presentinvention is depicted in FIG. 1. Referring to this figure, coatedabrasive article according to the present invention 1 has a backing(substrate) 2 and abrasive layer 3. Abrasive layer 3 includes abrasiveparticles according to the present invention 4 secured to a majorsurface of backing 2 by make coat 5 and size coat 6. In some instances,a supersize coat (not shown) is used.

Bonded abrasive articles typically include a shaped mass of abrasiveparticles held together by an organic, metallic, or vitrified binder.Such shaped mass can be, for example, in the form of a wheel, such as agrinding wheel or cutoff wheel. The diameter of grinding wheelstypically is about 1 cm to over 1 meter; the diameter of cut off wheelsabout 1 cm to over 80 cm (more typically 3 cm to about 50 cm). The cutoff wheel thickness is typically about 0.5 mm to about 5 cm, moretypically about 0.5 mm to about 2 cm. The shaped mass can also be in theform, for example, of a honing stone, segment, mounted point, disc (e.g.double disc grinder) or other conventional bonded abrasive shape. Bondedabrasive articles typically comprise about 3–50% by volume bondmaterial, about 30–90% by volume abrasive particles (or abrasiveparticle blends), up to 50% by volume additives (including grindingaids), and up to 70% by volume pores, based on the total volume of thebonded abrasive article.

A preferred form is a grinding wheel. Referring to FIG. 2, grindingwheel according to the present invention 10 is depicted, which includesabrasive particles according to the present invention 11, molded in awheel and mounted on hub 12.

Nonwoven abrasive articles typically include an open porous loftypolymer filament structure having abrasive particles according to thepresent invention distributed throughout the structure and adherentlybonded therein by an organic binder. Examples of filaments includepolyester fibers, polyamide fibers, and polyaramid fibers. In FIG. 3, aschematic depiction, enlarged about 100×, of a typical nonwoven abrasivearticle according to the present invention is provided. Such a nonwovenabrasive article according to the present invention comprises fibrousmat 50 as a substrate, onto which abrasive particles according to thepresent invention 52 are adhered by binder 54.

Useful abrasive brushes include those having a plurality of bristlesunitary with a backing (see, e.g., U.S. Pat. No. 5,427,595 (Pihl etal.), U.S. Pat. No. 5,443,906 (Pihl et al.), U.S. Pat. No. 5,679,067(Johnson et al.), and U.S. Pat. No. 5,903,951 (Ionta et al.), thedisclosure of which is incorporated herein by reference). Desirably,such brushes are made by injection molding a mixture of polymer andabrasive particles.

Suitable organic binders for making abrasive articles includethermosetting organic polymers. Examples of suitable thermosettingorganic polymers include phenolic resins, urea-formaldehyde resins,melamine-formaldehyde resins, urethane resins, acrylate resins,polyester resins, aminoplast resins having pendant α,β-unsaturatedcarbonyl groups, epoxy resins, acrylated urethane, acrylated epoxies,and combinations thereof. The binder and/or abrasive article may alsoinclude additives such as fibers, lubricants, wetting agents,thixotropic materials, surfactants, pigments, dyes, antistatic agents(e.g., carbon black, vanadium oxide, graphite, etc.), coupling agents(e.g., silanes, titanates, zircoaluminates, etc.), plasticizers,suspending agents, and the like. The amounts of these optional additivesare selected to provide the desired properties. The coupling agents canimprove adhesion to the abrasive particles and/or filler. The binderchemistry may thermally cured, radiation cured or combinations thereof.Additional details on binder chemistry may be found in U.S. Pat. No.4,588,419 (Caul et al.), U.S. Pat. No. 4,751,138 (Tumey et al.), andU.S. Pat. No. 5,436,063 (Follett et al.), the disclosures of which areincorporated herein by reference.

More specifically with regard to vitrified bonded abrasives, vitreousbonding materials, which exhibit an amorphous structure and aretypically hard, are well known in the art. In some cases, the vitreousbonding material includes crystalline phases. Bonded, vitrified abrasivearticles according to the present invention may be in the shape of awheel (including cut off wheels), honing stone, mounted pointed or otherconventional bonded abrasive shape. A preferred vitrified bondedabrasive article according to the present invention is a grinding wheel.

Examples of metal oxides that are used to form vitreous bondingmaterials include: silica, silicates, alumina, soda, calcia, potassia,titania, iron oxide, zinc oxide, lithium oxide, magnesia, boria,aluminum silicate, borosilicate glass, lithium aluminum silicate,combinations thereof, and the like. Typically, vitreous bondingmaterials can be formed from composition comprising from 10 to 100%glass frit, although more typically the composition comprises 20% to 80%glass frit, or 30% to 70% glass frit. The remaining portion of thevitreous bonding material can be a non-frit material. Alternatively, thevitreous bond may be derived from a non-frit containing composition.Vitreous bonding materials are typically matured at a temperature(s) ina range of about 700° C. to about 1500° C., usually in a range of about800° C. to about 1300° C., sometimes in a range of about 900° C. toabout 1200° C., or even in a range of about 950° C. to about 1100° C.The actual temperature at which the bond is matured depends, forexample, on the particular bond chemistry.

Preferred vitrified bonding materials may include those comprisingsilica, alumina (desirably, at least 10 percent by weight alumina), andboria (desirably, at least 10 percent by weight boria). In most casesthe vitrified bonding material further comprise alkali metal oxide(s)(e.g., Na₂O and K₂O) (in some cases at least 10 percent by weight alkalimetal oxide(s)).

Binder materials may also contain filler materials or grinding aids,typically in the form of a particulate material. Typically, theparticulate materials are inorganic materials. Examples of usefulfillers for this invention include: metal carbonates (e.g., calciumcarbonate (e.g., chalk, calcite, marl, travertine, marble andlimestone), calcium magnesium carbonate, sodium carbonate, magnesiumcarbonate), silica (e.g., quartz, glass beads, glass bubbles and glassfibers) silicates (e.g., talc, clays, (montmorillonite) feldspar, mica,calcium silicate, calcium metasilicate, sodium aluminosilicate, sodiumsilicate) metal sulfates (e.g., calcium sulfate, barium sulfate, sodiumsulfate, aluminum sodium sulfate, aluminum sulfate), gypsum,vermiculite, wood flour, aluminum trihydrate, carbon black, metal oxides(e.g., calcium oxide (lime), aluminum oxide, titanium dioxide), andmetal sulfites (e.g., calcium sulfite).

In general, the addition of a grinding aid increases the useful life ofthe abrasive article. A grinding aid is a material that has asignificant effect on the chemical and physical processes of abrading,which results in improved performance. Although not wanting to be boundby theory, it is believed that a grinding aid(s) will (a) decrease thefriction between the abrasive particles and the workpiece being abraded,(b) prevent the abrasive particles from “capping” (i.e., prevent metalparticles from becoming welded to the tops of the abrasive particles),or at least reduce the tendency of abrasive particles to cap, (c)decrease the interface temperature between the abrasive particles andthe workpiece, or (d) decreases the grinding forces.

Grinding aids encompass a wide variety of different materials and can beinorganic or organic based. Examples of chemical groups of grinding aidsinclude waxes, organic halide compounds, halide salts and metals andtheir alloys. The organic halide compounds will typically break downduring abrading and release a halogen acid or a gaseous halide compound.Examples of such materials include chlorinated waxes liketetrachloronaphtalene, pentachloronaphthalene, and polyvinyl chloride.Examples of halide salts include sodium chloride, potassium cryolite,sodium cryolite, ammonium cryolite, potassium tetrafluoroboate, sodiumtetrafluoroborate, silicon fluorides, potassium chloride, and magnesiumchloride. Examples of metals include, tin, lead, bismuth, cobalt,antimony, cadmium, and iron titanium. Other miscellaneous grinding aidsinclude sulfur, organic sulfur compounds, graphite, and metallicsulfides. It is also within the scope of the present invention to use acombination of different grinding aids, and in some instances this mayproduce a synergistic effect. The preferred grinding aid is cryolite;the most preferred grinding aid is potassium tetrafluoroborate.

Grinding aids can be particularly useful in coated abrasive and bondedabrasive articles. In coated abrasive articles, grinding aid istypically used in the supersize coat, which is applied over the surfaceof the abrasive particles. Sometimes, however, the grinding aid is addedto the size coat. Typically, the amount of grinding aid incorporatedinto coated abrasive articles are about 50–300 g/m² (desirably, about80–160 g/m²). In vitrified bonded abrasive articles grinding aid istypically impregnated into the pores of the article.

The abrasive articles can contain 100% abrasive particles according tothe present invention, or blends of such abrasive particles with otherabrasive particles and/or diluent particles. However, at least about 2%by weight, desirably at least about 5% by weight, and more desirablyabout 30–100% by weight, of the abrasive particles in the abrasivearticles should be abrasive particles according to the presentinvention. In some instances, the abrasive particles according thepresent invention may be blended with another abrasive particles and/ordiluent particles at a ratio between 5 to 75% by weight, about 25 to 75%by weight about 40 to 60% by weight, or about 50% to 50% by weight(i.e., in equal amounts by weight). Examples of suitable conventionalabrasive particles include fused aluminum oxide (including white fusedalumina, heat-treated aluminum oxide and brown aluminum oxide), siliconcarbide, boron carbide, titanium carbide, diamond, cubic boron nitride,garnet, fused alumina-zirconia, and sol-gel-derived abrasive particles,and the like. The sol-gel-derived abrasive particles may be seeded ornon-seeded. Likewise, the sol-gel-derived abrasive particles may berandomly shaped or have a shape associated with them, such as a rod or atriangle. Examples of sol gel abrasive particles include those describedU.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat. No. 4,518,397(Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer et al.), U.S.Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe et al.),U.S. Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No. 5,011,508 (Wald etal.), U.S. Pat. No. 5,090,968 (Pellow), U.S. Pat. No. 5,139,978 (Wood),U.S. Pat. No. 5,201,916 (Berg et al.), U.S. Pat. No. 5,227,104 (Bauer),U.S. Pat. No. 5,366,523 (Rowenhorst et al.), U.S. Pat. No. 5,429,647(Larmie), U.S. Pat. No. 5,498,269 (Larmie), and U.S. Pat. No. 5,551,963(Larmie), the disclosures of which are incorporated herein by reference.Additional details concerning sintered alumina abrasive particles madeby using alumina powders as a raw material source can also be found, forexample, in U.S. Pat. No. 5,259,147 (Falz), U.S. Pat. No. 5,593,467(Monroe), and U.S. Pat. No. 5,665,127 (Moltgen), the disclosures ofwhich are incorporated herein by reference. Additional detailsconcerning fused abrasive particles, can be found, for example, in U.S.Pat. No. 1,161,620 (Coulter), U.S. Pat. No. 1,192,709 (Tone), U.S. Pat.No. 1,247,337 (Saunders et al.), U.S. Pat. No. 1,268,533 (Allen), andU.S. Pat. No. 2,424,645 (Baumann et al.), U.S. Pat. No. 3,891,408 (Rowseet al.), U.S. Pat. No 3,781,172 (Pett et al.), U.S. Pat. No. 3,893,826(Quinan et al.), U.S. Pat. No. 4,126,429 (Watson), U.S. Pat. No.4,457,767 (Poon et al.), U.S. Pat. No. 5,023,212 (Dubots et. al), U.S.Pat. No. 5,143,522 (Gibson et al.), and U.S. Pat. No. 5,336,280 (Dubotset al.), and applications having U.S. Serial Nos. 09,495,978,09/496,422, 09/496,638, and 09/496,713, each filed on Feb. 2, 2000, and,Ser. Nos. 09/618,876, 09/618,879, 09/619,106, 09/619,191, 09/619,192,09/619,215, 09/619,289, 09/619,563, 09/619,729, 09/619,744, and09/620,262, each filed on Jul. 19, 2000, and Ser. No. 09/772,730, filedJan. 30, 2001, the disclosures of which are incorporated herein byreference. In some instances, blends of abrasive particles may result inan abrasive article that exhibits improved grinding performance incomparison with abrasive articles comprising 100% of either type ofabrasive particle.

If there is a blend of abrasive particles, the abrasive particle typesforming the blend may be of the same size. Alternatively, the abrasiveparticle types may be of different particle sizes. For example, thelarger sized abrasive particles may be abrasive particles according tothe present invention, with the smaller sized particles being anotherabrasive particle type. Conversely, for example, the smaller sizedabrasive particles may be abrasive particles according to the presentinvention, with the larger sized particles being another abrasiveparticle type.

Examples of suitable diluent particles include marble, gypsum, flint,silica, iron oxide, aluminum silicate, glass (including glass bubblesand glass beads), alumina bubbles, alumina beads and diluentagglomerates. Abrasive particles according to the present invention canalso be combined in or with abrasive agglomerates. Abrasive agglomerateparticles typically comprise a plurality of abrasive particles, abinder, and optional additives. The binder may be organic and/orinorganic. Abrasive agglomerates may be randomly shape or have apredetermined shape associated with them. The shape may be a block,cylinder, pyramid, coin, square, or the like. Abrasive agglomerateparticles typically have particle sizes ranging from about 100 to about5000 micrometers, typically about 250 to about 2500 micrometers.Additional details regarding abrasive agglomerate particles may befound, for example, in U.S. Pat. No. 4,311,489 (Kressner), U.S. Pat. No.4,652,275 (Bloecher et al.), U.S. Pat. No. 4,799,939 (Bloecher et al.),U.S. Pat. No. 5,549,962 (Holmes et al.), and U.S. Pat. No. 5,975,988(Christianson), and applications having U.S. Ser. Nos. 09/688,444 and09/688,484, filed Oct. 16, 2000, the disclosures of which areincorporated herein by reference.

The abrasive particles may be uniformly distributed in the abrasivearticle or concentrated in selected areas or portions of the abrasivearticle. For example, in a coated abrasive, there may be two layers ofabrasive particles. The first layer comprises abrasive particles otherthan abrasive particles according to the present invention, and thesecond (outermost) layer comprises abrasive particles according to thepresent invention. Likewise in a bonded abrasive, there may be twodistinct sections of the grinding wheel. The outermost section maycomprise abrasive particles according to the present invention, whereasthe innermost section does not. Alternatively, abrasive particlesaccording to the present invention may be uniformly distributedthroughout the bonded abrasive article.

Further details regarding coated abrasive articles can be found, forexample, in U.S. Pat. No. 4,734,104 (Broberg), U.S. Pat. No. 4,737,163(Larkey), U.S. Pat. No. 5,203,884 (Buchanan et al.), U.S. Pat. No.5,152,917 (Pieper et al.), U.S. Pat. No. 5,378,251 (Culler et al.), U.S.Pat. No. 5,417,726 (Stout et al.), U.S. Pat. No. 5,436,063 (Follett etal.), U.S. Pat. No. 5,496,386 (Broberg et al.), U.S. Pat. No. 5, 609,706(Benedict et al.), U.S. Pat. No. 5,520,711 (Helmin), U.S. Pat. No.5,954,844 (Law et al.), U.S. Pat. No. 5,961,674 (Gagliardi et al.), andU.S. Pat. No. 5,975,988 (Christianson), the disclosures of which areincorporated herein by reference. Further details regarding bondedabrasive articles can be found, for example, in U.S. Pat. No. 4,543,107(Rue), U.S. Pat. No. 4,741,743 (Narayanan et al.), U.S. Pat. No.4,800,685 (Haynes et al.), U.S. Pat. No. 4,898,597 (Hay et al.), U.S.Pat. No. 4,997,461 (Markhoff-Matheny et al.), U.S. Pat. No. 5,037,453(Narayanan et al.), U.S. Pat. No. 5,110,332 (Narayanan et al.), and U.S.Pat. No. 5,863,308 (Qi et al.) the disclosures of which are incorporatedherein by reference. Further details regarding vitreous bonded abrasivescan be found, for example, in U.S. Pat. No. 4,543,107 (Rue), U.S. Pat.No. 4,898,597 (Hay et al.), U.S. Pat. No. 4,997,461 (Markhoff-Matheny etal.), U.S. Pat. No. 5,094,672 (Giles Jr. et al.), U.S. Pat. No.5,118,326 (Sheldon et al.), 5,131,926 (Sheldon et al.), U.S. Pat. No.5,203,886 (Sheldon et al.), U.S. Pat. No. 5,282,875 (Wood et al.), U.S.Pat. No. 5,738,696 (Wu et al.), and U.S. Pat. No. 5,863,308 (Qi), thedisclosures of which are incorporated herein by reference. Furtherdetails regarding nonwoven abrasive articles can be found, for example,in U.S. Pat. No. 2,958,593 (Hoover et al.), the disclosure of which isincorporated herein by reference.

The present invention provides a method of abrading a surface, themethod comprising contacting at least one abrasive particle according tothe present invention, with a surface of a workpiece; and moving atleast of one the abrasive particle or the contacted surface to the otherto abrade at least a portion of said surface with the abrasive particle.Methods for abrading with abrasive particles according to the presentinvention range of snagging (i.e., high pressure high stock removal) topolishing (e.g., polishing medical implants with coated abrasive belts),wherein the latter is typically done with finer grades (e.g., less ANSI220 and finer) of abrasive particles. The abrasive particle may also beused in precision abrading applications, such as grinding cam shaftswith vitrified bonded wheels. The size of the abrasive particles usedfor a particular abrading application will be apparent to those skilledin the art.

Abrading with abrasive particles according to the present invention maybe done dry or wet. For wet abrading, the liquid may be introducedsupplied in the form of a light mist to complete flood. Examples ofcommonly used liquids include: water, water-soluble oil, organiclubricant, and emulsions. The liquid may serve to reduce the heatassociated with abrading and/or act as a lubricant. The liquid maycontain minor amounts of additives such as bactericide, antifoamingagents, and the like.

Abrasive particles according to the present invention may be used toabrade workpieces such as aluminum metal, carbon steels, mild steels,tool steels, stainless steel, hardened steel, titanium, glass, ceramics,wood, wood like materials, paint, painted surfaces, organic coatedsurfaces and the like. The applied force during abrading typicallyranges from about 1 to about 100 kilograms.

Other examples of uses of embodiments of amorphous materials and/orglass-ceramics according to the present invention include as solidelectrolytes in such applications as solid state batteries, solid oxidefuel cells and other electrochemical devices; as hosts for radioactivewastes and surplus actinides; as oxidation catalysts; as oxygenmonitoring sensors; as hosts for fluorescence centers; durable IRtransmitting window materials; and armor. For example, pyrochlore typeof rare earth zirconium oxides (Re₂Zr₂O₇) are known to be useful phasesfor the above-mentioned radioactive wastes, surplus actinides, oxidationcatalysts, oxygen monitoring sensors, and fluorescence centersapplications. Further, for example, Ce-containing mixed oxides are knownas oxidation catalysts. Although not wanting to be bound by theory, itis believed that the redox properties and the relatively high oxygenstorage capacity of the Ce-containing mixed oxides aid in oxidationcatalysts. With regard to durable IR transmitting window materialsapplications uses include those involving moisture, impact by solid andliquid particles, high temperatures, and rapid heating rates.

Advantages and embodiments of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. All parts andpercentages are by weight unless otherwise indicated. Unless otherwisestated, all examples contained no significant amount of SiO₂, B₂O₃,P₂O₅, GeO₂, TeO₂, As₂O₃, and V₂O₅.

EXAMPLES Example 1

A 250-ml polyethylene bottle (7.3-cm diameter) was charged with thefollowing 50-gram mixture: 19.3 grams of alumina particles (obtainedfrom Alcoa Industrial Chemicals, Bauxite, Ark., under the tradedesignation “A16SG”), 9.5 grams of zirconium oxide particles (obtainedfrom Zirconia Sales, Inc. of Marietta, Ga. under the trade designation“DK-2”), and 21.2 grams of lanthanum oxide particles (obtained fromMolycorp Inc., Mountain Pass, Calif.), 75 grams of isopropyl alcohol,and 200 grams of alumina milling media (cylindrical in shape, bothheight and diameter of 0.635 cm; 99.9% alumina; obtained from Coors,Golden, Colo.). The contents of the polyethylene bottle were milled for16 hours at 60 revolutions per minute (rpm). The ratio of alumina tozirconia in the starting material was 2:1, and the alumina and zirconiacollectively made up about 58 weight percent (wt-%). After the milling,the milling media were removed and the slurry was poured onto a warm(approximately 75° C.) glass (“PYREX”) pan and dried. The dried mixturewas screened through a 70-mesh screen (212-micrometer opening size) withthe aid of a paint brush.

After grinding and screening, the mixture of milled feed particles wasfed slowly (0.5 gram/minute) into a hydrogen/oxygen torch flame to meltthe particles. The torch used to melt the particles, thereby generatingmolten droplets, was a Bethlehem bench burner PM2D Model B obtained fromBethlehem Apparatus Co., Hellertown, Pa. Hydrogen and oxygen flow ratesfor the torch were as follows. For the inner ring, the hydrogen flowrate was 8 standard liters per minute (SLPM) and the oxygen flow ratewas 3.5 SLPM. For the outer ring, the hydrogen flow rate was 23 SLPM andthe oxygen flow rate was 12 SLPM. The dried and sized particles were fedslowly (0.5 gram/minute) into the torch flame, which melted theparticles and carried them on to an inclined stainless steel surface(approximately 51 centimeters (20 inches) wide with a slope angle of 45degrees) with cold water running over (approximately 8 liters/minute)the surface to rapidly quench the molten droplets. The resulting moltenand quenched beads were collected and dried at 110° C. The particleswere spherical in shape and varied in size from a few micrometers (i.e.,microns) up to 250 micrometers.

Subsequently, the flame-formed beads having diameters less than 125micrometers were then passed through a plasma gun and deposited onstainless steel substrates as follows.

Four 304 stainless steel substrates (76.2 millimeter (mm)×25.4 mm×3.175mm dimensions), and two 1080 carbon steel substrates (76.2 mm×25.4mm×1.15 mm) were prepared in the following manner. The sides to becoated were sandblasted, washed in an ultrasonic bath, and then wipedclean with isopropyl alcohol. Four stainless steel and one 1080 carbonsteel substrates were placed approximately 10 centimeters (cm) in frontof the nozzle of a plasma gun (obtained under the trade designation“Praxair SG-100 Plasma Gun” from Praxair Surface Technologies, Concord,N.H.). The second 1080 carbon steel was placed 18 cm in front of thenozzle of the plasma gun. The coatings made on the second 1080 carbonsteel samples at a distance of 18 cm in front of the nozzle of theplasma gun were not further characterized.

The plasma unit had a power rating of 40 kW. The plasma gas was argon(50 pounds per square inch (psi), 0.3 megapascal (MPa)) with helium asthe auxiliary gas (150 psi, 1 MPa). The beads were passed through theplasma gun by using argon as the carrier gas (50 psi, 0.3 MPa) using aPraxair Model 1270 computerized powder feeder (obtained from PraxairSurface Technologies, Concord, N.H.). During deposition, a potential ofabout 40 volts and a current of about 900 amperes was applied and theplasma gun was panned left to right, up and down, to evenly coat thesubstrates. When the desired thickness was achieved, the plasma spraywas shut off and the samples were recovered. The 1080 carbon steelsubstrate was flexed, thus separating the coating from the substrateresulting in a free-standing bulk material. The deposited material had az dimension (thickness) of about 1350 micrometers, as determined usingoptical microscopy.

The phase composition (glassy/amorphous/crystalline) was determinedthrough Differential Thermal Analysis (DTA) as described below. Thematerial was classified as amorphous if the corresponding DTA trace ofthe material contained an exothermic crystallization event (T_(x)). Ifthe same trace also contained an endothermic event (T_(g)) at atemperature lower than T_(x) it was considered to consist of a glassphase. If the DTA trace of the material contained no such events, it wasconsidered to contain crystalline phases.

Differential thermal analysis (DTA) was conducted using the followingmethod. DTA runs were made (using an instrument obtained from NetzschInstruments, Selb, Germany under the trade designation “NETZSCH STA 409DTA/TGA”) using a −140+170 mesh size fraction (i.e., the fractioncollected between 105-micrometer opening size and 90-micrometer openingsize screens). The amount of each screened sample placed in a100-microliter Al₂O₃ sample holder was about 400 milligrams. Each samplewas heated in static air at a rate of 10° C./minute from roomtemperature (about 25° C.) to 1100° C.

The coated material (on 304 stainless steel substrates) exhibited anendothermic event at a temperature around 880° C., as evidenced by adownward change in the curve of the trace. It is believed this event wasdue to the glass transition (T_(g)) of the glass material. The samematerial exhibited an exothermic event at a temperature around 931° C.,as evidenced by a sharp peak in the trace. It is believed that thisevent was due to the crystallization (T_(x)) of the material. Thus, thecoated material (on 304 stainless steel substrates) and thefree-standing bulk material were glassy as determined by a DTA trace.

A portion of the glassy free-standing bulk material was thenheat-treated at 1300° C. for 48 hours. Powder X-ray diffraction, XRD,(using an X-ray diffractometer (obtained under the trade designation“PHILLIPS XRG 3100” from Phillips, Mahwah, N.J.) with copper K α1radiation of 1.54050 Angstrom)) was used to determine the phasespresent. The phases were determined by comparing the peaks present inthe XRD trace of the crystallized material to XRD patterns ofcrystalline phases provided in JCPDS databases, published byInternational Center for Diffraction Data. The resulting crystallinematerial included LaAlO₃, ZrO₂ (cubic, tetragonal), LaAl₁₁O₁₈, andtransitional Al₂O₃ phases.

Another portion of the glassy free-standing bulk material wascrystallized at 1300° C. for 1 hour in an electrically heated furnace(obtained from CM Furnaces, Bloomfield, N.J. under the trade designation“Rapid Temp Furnace”). The crystallized coating was crushed with ahammer into particles of −30+35 mesh size (i.e., the fraction collectedbetween 600-micrometer opening size and 500-micrometer opening sizescreens). The particles were cleaned of debris by washing in a sonicbath (obtained from Cole-Parmer, Vernon Hills, Ill., under the tradedesignation “8891”) for 15 minutes, dried at 100° C., and several weremounted on a metal cylinder (3 cm in diameter and 2 cm high) usingcarbon tape. The mounted sample was sputter coated with a thin layer ofgold-palladium and viewed using a JEOL scanning electron microscopy(SEM) (Model JSM 840A). The fractured surface was rough and no crystalscoarser than 200 nanometers (nm) were observed (see FIG. 4) in the SEM.

Example 2

Feed particles were made as described in Example 1 using the following50-gram mixture: 21.5 grams of alumina particles (obtained from AlcoaIndustrial Chemicals, Bauxite, Ark. under the trade designation“A16SG”), 9 grams of zirconium oxide particles (obtained from ZirconiaSales, Inc. of Marietta, Ga. under the trade designation “DK-2”), and19.5 grams of cerium oxide particles (obtained from Rhone-Poulence,France). The ratio of alumina to zirconia in the starting material was2.4:1 and the alumina and zirconia collectively made up about 61 weightpercent. Feed particles were flame-formed into beads (of a size thatvaried from a few micrometers up to 250 micrometers) as described inExample 1. Subsequently, the flame-formed beads having diameters between180 micrometers and 250 micrometers were sprayed through a plasma gunand deposited on stainless and carbon steel substrates as described inExample 1.

The 1080 carbon steel substrates were flexed, thus separating thecoating from the substrate resulting in a free-standing bulk material.The resulting bulk material had a z dimension (thickness) of about 700micrometers, as determined using optical microscopy. The microstructurewas also observed using optical microscopy. The material consisted ofgenerally spherical and oblique crystalline particles, which wereopaque, within a predominantly amorphous matrix, which was transparent.Amorphous material is typically transparent due to the lack of lightscattering centers such as crystal boundaries, while the crystallineparticles show a crystalline structure and are opaque due to lightscattering effects. The crystalline phases, determined by powder XRDanalysis as described in Example 1, consisted of Zr₀₄Ce_(0.6)O₂ (cubic)and transitional Al₂O₃.

A second deposition experiment was carried out using the flame-formedbeads having diameters less than 125 micrometers. The resulting coatinghad a z dimension (thickness) of about 1100 micrometers, as determinedusing optical microscopy. The microstructure was also observed usingoptical microscopy. This material had similar features (i.e., consistedof generally spherical and oblique crystalline particles within apredominantly amorphous matrix) to those of the material formed frombeads having diameters between 180 micrometers and 250 micrometers. Thecrystalline phases, determined by XRD analysis as described in Example1, consisted of Zr_(0.4)Ce_(0.6)O₂ (cubic) and transitional Al₂O₃.

The average hardness of the as-sprayed material of this example wasdetermined as follows. Sections of the material were mounted in mountingresin (obtained under the trade designation “TRANSOPTIC POWDER” fromBuehler, Lake Bluff, Ill.). The resulting cylinder of resin was about2.5 cm in diameter and about 1.9 cm high. The mounted section wasprepared using conventional polishing techniques using a polisher(obtained from Buehler, Lake Bluff, Ill. under the trade designation“ECOMET 3”). The sample was polished for about 3 minutes with a diamondwheel, followed by 5 minutes of polishing with each of 45, 30, 15, 9, 3,and 1-micrometer slurries. The microhardness measurements were madeusing a conventional microhardness tester (obtained under the tradedesignation “MITUTOYO MVK-VL” from Mitutoyo Corporation, Tokyo, Japan)fitted with a Vickers indenter using a 100-gram indent load. Themicrohardness measurements were made according to the guidelines statedin ASTM Test Method E384 Test Methods for Microhardness of Materials(1991), the disclosure of which is incorporated herein by reference. Theaverage microhardness (an average of 20 measurements) of the material ofthis example was 15 gigapascals (Gpa).

Example 3

Feed particles were made as described in Example 1 using the following50-gram mixture: 27.9 grams of alumina particles (obtained from AlcoaIndustrial Chemicals, Bauxite, Ark. under the trade designation“A16SG”), 7.8 grams of zirconium oxide particles (obtained from ZirconiaSales, Inc. of Marietta, Ga. under the trade designation “DK-2”), and14.3 grams of yttrium oxide particles (obtained from H. C. Stark Newton,Mass.). The ratio of alumina to zirconia of initial starting materialswas 3.5:1 and the alumina and zirconia collectively made up about 72weight percent. The feed particles were then screened through a 30-meshscreen (600-micrometer opening size) and heat-treated at 1400° C. for 2hours in an electrically heated furnace (obtained from CM Furnaces,Bloomfield, N.J. under the trade designation “Rapid Temp Furnace”). Theheat-treated particles were further screened to separate out particleswith diameters between 125 micrometers and 180 micrometers, which werethen passed through a plasma gun and deposited on stainless steelsubstrates as described in Example 1.

The 1080 carbon steel substrate was flexed, thus separating the coatingfrom the substrate resulting in a free-standing bulk material. Theresulting bulk material had a z dimension (thickness) of about 700micrometers, as determined using optical microscopy. The microstructurewas observed using optical microscopy. This material consisted ofgenerally crystalline opaque particles (which mostly retained theiroriginal angular shapes) within a predominantly transparent, amorphousmatrix. The crystalline phases, determined by powder XRD analysis asdescribed in Example 1, consisted of Al₅Y₃O₁₂ and Y_(0.15)Zr₀₈₅O₁₉₃.

Another portion of the free-standing bulk material was crystallized at1300° C. for 1 hour and the fractured surface was sputter coated with athin layer of gold-palladium and viewed using a JEOL SEM (Model JSM840A), as described above in Example 1. The fractured surface was roughand no crystals coarser than 200 nm were observed (see FIG. 5).

A second deposition experiment was carried out using heat-treatedparticles having diameters less than 125 micrometers. The resultingcoating was about 1500 micrometers thick (z dimension). Themicrostructure was observed using optical microscopy. This material hadsimilar features (consisted of generally opaque, crystalline particles(which mostly retained their original angular shapes) within apredominantly transparent, amorphous matrix) to the material formed frombeads having diameters between 180 micrometers and 250 micrometers. Thecrystalline phases, determined by XRD analysis as described in Example1, consisted of Al₅Y₃O₁₂ and Y₀₁₅Zr₀₈₅O₁₉₃.

Example 4

A thick coating consisting of various layers of the above three exampleswas plasma sprayed using feed particles produced in Examples 1–3. Thefirst layer was coated as described in Example 2, the second asdescribed in Example 1, and the third as described in Example 3.

The substrate was not sandblasted prior to coating so that it wasremoved easily by plying it apart by hand, resulting in a free-standingbulk material, approximately 75 millimeters (mm)×25 mm×7.5 mm. Across-section, cutting through each layer, was sectioned from thematerial using a diamond saw. The sectioned piece was mounted inmounting resin (obtained under the trade designation “TRANSOPTIC POWDER”from Buehler, Lake Bluff, 1L) such that the different layers werevisible. The resulting cylinder of resin was about 2.5 cm in diameterand about 1.9 cm tall (i.e., high). The mounted section was preparedusing conventional polishing techniques using a polisher (obtained fromBuehler, Lake Bluff, Ill. under the trade designation “ECOMET 3”). Thesample was polished for about 3 minutes with a diamond wheel, followedby 5 minutes of polishing with each of 45, 30, 15, 9, 3, and1-micrometer slurries.

The first layer had a z dimension (thickness) of approximately 2.5 mm,as determined using optical microscopy. The microstructure was observedusing optical microscopy. This material had similar features to those ofthe material of Example 2 (i.e., consisted of generally spherical andopaque crystalline particles within a predominantly transparent,amorphous matrix). The second layer had a z dimension (thickness) ofapproximately 2 mm, as determined using optical microscopy. Themicrostructure was also observed using optical microscopy. This materialhad similar features to those of the material of Example 1 (i.e., wastransparent suggesting it was amorphous). The third layer had a zdimension (thickness) of approximately 3 mm, as determined using opticalmicroscopy. The microstructure was also observed using opticalmicroscopy. This material had similar features to those of the materialof Example 3 (i.e., it consisted of generally opaque crystallineparticles (which mostly retained their original angular shapes) within apredominantly transparent, amorphous matrix).

Examples 5–7

Feed particles were made as described in Example 1, except the mixturesused were those listed in Table 1, below, with the raw material sourceslisted in Table 2, below. Feed particles were flame formed into beads asdescribed in Example 1.

A percent amorphous yield was calculated from the resulting flame-formedbeads using a −100+120 mesh size fraction (i.e., the fraction collectedbetween 150-micrometer opening size and 125-micrometer opening sizescreens). The measurements were done in the following manner. A singlelayer of beads was spread out upon a glass slide. The beads wereobserved using an optical microscope. Using the crosshairs in theoptical microscope eyepiece as a guide, beads that lay along a straightline were counted either amorphous or crystalline depending on theiroptical clarity. A total of 500 beads were counted and a percentamorphous yield was determined by the amount of amorphous beads dividedby total beads counted. For the examples, DTA was conducted as describedin Example 1. The T_(g) and T_(x) values for certain examples arereported in Table 1, below.

TABLE 1 Weight Percent Glass transition/ Batch percent of amorphouscrystallization Example amounts, g components yield temperatures Ex. 5Al₂O₃: 19.3 Al₂O₃: 38.5 98 La₂O₃: 21.2 La₂O₃: 42.5 882° C. ZrO₂: 9.5ZrO₂: 19.0 932° C. Ex. 6 Al₂O₃: 20.5 Al₂O₃: 41.0 94 872° C. Gd₂O₃: 20.5Gd₂O₃: 41.0 932° C. ZrO₂: 9 ZrO₂: 18 Ex. 7 Al₂O₃: 16.7 Al₂O₃: 33.3 89900° C. Al: 8.8 Al: 17.6 935° C. Y₂O₃: 16 Y₂O₃: 31.9 ZrO₂: 8.6 ZrO₂:17.2

TABLE 2 Raw Material Source Alumina particles Obtained from AlcoaIndustrial Chemicals, (Al₂O₃) Bauxite, AR, under the trade designation“Al6SG” Aluminum particles (Al) Obtained from Alfa Aesar, Ward Hill, MALanthanum oxide Obtained from Molycorp Inc., Mountain Pass, particles(La₂O₃) CA and calcined at 700° C. for 6 hours prior to batch mixingGadolinium oxide Obtained from Molycorp Inc., Mountain Pass, particles(Gd₂O₃) CA Yttrium oxide particles Obtained from H. C. Stark Newton, MA(Y₂O₃) Zirconium oxide particles Obtained from Zirconia Sales, Inc. ofMarietta, (ZrO₂) GA under the trade designation “DK-2”

About 25 grams of the beads from Example 5 were placed in a graphite dieand hot-pressed using a uniaxial pressing apparatus (obtained under thetrade designation “HP-50”, Thermal Technology Inc., Brea, Calif.). Thehot pressing was carried out in an argon atmosphere and 13.8 megapascals(MPa) (2000 pounds per square inch or 2 ksi) pressure. The hot pressingfurnace was ramped up to 970° C. at 25° C./minute. The resultingtransparent disk, approximately 34 mm in diameter, 6 mm in thickness,was crushed by using a “Chipmunk” jaw crusher (Type VD, manufactured byBICO Inc., Burbank, Calif.) into abrasive particles and graded to retainthe −30+35 fraction (i.e., the fraction collected between 600-micrometeropening size and 500-micrometer opening size screens) and the −35+40mesh fraction (i.e., the fraction collected between 500-micrometeropening size and 425-micrometer opening size screens). The gradedabrasive particles were crystallized by heat-treating at 1300° C. for 45minutes in an electrically heated furnace. The crystalline phases,determined by XRD analysis as described in Example 1, included LaAlO₃,ZrO₂ (cubic, tetragonal), LaAl₁₁O₁₈, and transitional Al₂O₃ phases.

A second hot press disk of the material prepared in Example 5 was madeas described above. The disk was crystallized by heat-treating at 1300°C. for 45 minutes in an electrically heated furnace. The crystallinephases, determined by XRD analysis as described in Example 1, includedLaAlO₃, ZrO₂ (cubic, tetragonal), LaAl₁₁O₁₈, and transitional Al₂O₃phases. The crystallized disk was crushed by using a “Chipmunk” jawcrusher (Type VD, manufactured by BICO Inc., Burbank, CA) into abrasiveparticles and graded to retain the −30+35 fraction (i.e., the fractioncollected between 600-micrometer opening size and 500-micrometer openingsize screens) and the −35+40 mesh fraction (i.e., the fraction collectedbetween 500-micrometer opening size and 425-micrometer opening sizescreens).

The average microhardness of the heat-treated, graded particles wasmeasured by mounting the particles in mounting resin (obtained under thetrade designation “EPOMET” from Buehler Ltd., Lake Bluff, Ill.). Theresulting cylinder of resin was about 2.5 cm (1 inch) in diameter andabout 1.9 cm (0.75 inch) high. The mounted samples were polished using aconventional grinder/polisher (obtained under the trade designation“EPOMET” from Buehler Ltd.) and conventional diamond slurries with thefinal polishing step using a 1 micrometer diamond slurry (obtained underthe trade designation “METADI” from Buehler Ltd.) to obtain polishedcross-sections of the sample. The microhardness measurements were madeusing a conventional microhardness tester (obtained under the tradedesignation “MITUTOYO MVK-VL” from Mitutoyo Corporation, Tokyo, Japan)fitted with a Vickers indenter using a 500-gram indent load. Themicrohardness measurements were made according to the guidelines statedin ASTM Test Method E384 Test Methods for Microhardness of Materials(1991), the disclosure of which is incorporated herein by reference. Themicrohardness values were an average of 20 measurements. The averagemicrohardness of the particles was 17.6 GPa.

Example 8

About 150 grams of the beads prepared as described in Example 5 wereplaced in a 5 centimeter (cm)×5 cm×5 cm steel can, which was thenevacuated and sealed from the atmosphere. The steel can was subsequentlyhot-isostatically pressed (HIPed) using a HIP apparatus (obtained underthe trade designation “IPS Eagle-6”, American Isostatic Pressing, Ohio).The HIPing was carried out at 207 MPa (30 ksi) pressure in an argonatmosphere. The HIPing furnace was ramped up to 970° C. at 25C./minuteand held at that temperature for 30 minutes. After the HIPing, the steelcan was cut and the charge material removed. It was observed that beadscoalesced into a chunk of transparent, glassy material. The DTA trace,conducted as described in Example 1, exhibited a glass transition(T_(g)) of 879° C. and a crystallization temperature (T_(x)) of 931° C.

Examples 9–19

A 250-ml polyethylene bottle (7.3-cm diameter) was charged with a50-gram mixture of various powders (as shown below in Table 3, below,with sources of the raw materials listed in Table 4, below), 75 grams ofisopropyl alcohol, and 200 grams of alumina milling media (cylindricalshape, both height and diameter of 0.635 cm; 99.9% alumina; obtainedfrom Coors, Golden, Colo.). The contents of the polyethylene bottle weremilled for 16 hours at 60 revolutions per minute (rpm). After themilling, the milling media were removed and the slurry was poured onto awarm (approximately 75° C.) glass (“PYREX”) pan and dried. The driedmixture was screened through a 70-mesh screen (212-micrometer openingsize) with the aid of a paint brush.

After grinding and screening, the mixture of milled feed particles wasfed slowly (0.5 gram/minute) into a hydrogen/oxygen torch flame to meltthe particles. The torch used to melt the particles, thereby generatingmolten droplets, was a Bethlehem bench burner PM2D Model B obtained fromBethlehem Apparatus Co., Hellertown, Pa. Hydrogen and oxygen flow ratesfor the torch were as follows. For the inner ring, the hydrogen flowrate was 8 standard liters per minute (SLPM) and the oxygen flow ratewas 3.5 SLPM. For the outer ring, the hydrogen flow rate was 23 SLPM andthe oxygen flow rate was 12 SLPM. The dried and sized particles were fedslowly (0.5 gram/minute) into the torch flame which melted the particlesand carried them into a 19-liter (5-gallon) cylindrical container (30 cmdiameter by 34 cm height) of continuously circulating, turbulent waterto rapidly quench the molten droplets. The angle at which the flame hitthe water was approximately 45°, and the flame length, burner to watersurface, was approximately 18 centimeters (cm). The resulting molten andrapidly quenched particles were collected and dried at 110° C. Theparticles were spherical in shape and varied in size from a fewmicrometers (i.e., microns) up to 250 micrometers.

For certain examples, a percent amorphous yield was calculated asdescribed in Examples 5–7. For certain examples, DTA was conducted asdescribed in Example 1. The T_(g) and T_(x) values for certain examplesare reported in Table 3, below.

Materials prepared in Examples 15 through 22 were amorphous asdetermined by visual inspection using optical microscopy. Quantitativeanalysis according to the above procedure was not performed.

TABLE 3 Percent final Percent Glass transition/ Batch Weight percentFinal weight alumina from Al amorphous crystallization Example amounts,g of components percent alumina % metal yield temperatures Ex. 9 Al₂O₃:15.5 Al₂O₃: 31.0 AZ-Ti Al: 8.2 Al: 16.4 ZrO₂: 22.0 ZrO₂: 44.0 none TiO₂:4.3 TiO₂: 8.6 54 50 79 936° C. Ex. 10 Al₂O₃: 12.3 Al₂O₃: 24.5 AZ-La Al:6.5 Al: 13.0 ZrO₂: 17.4 ZrO₂: 34.8 889° C. La₂O₃: 13.8 La₂O₃: 27.7 44 5094 918° C. Ex. 11 Al₂O₃: 9.1 Al₂O₃: 18.2 AZ-La Al: 4.8 Al: 9.6 ZrO₂:13.0 ZrO₂: 25.9 868° C. La₂O₃: 23.1 La₂O₃: 46.2 34 50 96 907° C. Ex. 12Al₂O₃: 7.5 Al₂O₃: 15.0 28 50 93 870° C. AZ-La Al: 4.0 Al: 8.0 898° C.ZrO₂: 17.0 ZrO₂: 34.0 La₂O₃21.4 La₂O₃42.8 Ex. 13 Al₂O₃: 17.87 Al₂O₃:35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 P₂O₅ ZrO₂: 8.55 ZrO₂: 17.1 P₂O₅:2.5 P₂O₅: 5 857° C. 35.73 0  NA* 932° C. Ex. 14 Al₂O₃: 17.87 Al₂O₃:35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 Nb₂O₅ ZrO₂: 8.55 ZrO₂: 17.1 Nb₂O₅:2.5 Nb₂O₅: 5 35.73 0 NA NA Ex. 15 Al₂O₃: 17.87 Al₂O₃: 35.73 ALZ/ La₂O₃:21.08 La₂O₃: 42.17 Ta₂O₅ ZrO₂: 8.55 ZrO₂: 17.1 Ta₂O₅: 2.5 Ta₂O₅: 5 35.730 NA NA Ex. 16 Al₂O₃: 17.87 Al₂O₃: 35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17SrO ZrO₂: 8.55 ZrO₂: 17.1 SrO: 2.5 SrO: 5 35.73 0 NA NA Ex. 17 Al₂O₃:17.87 Al₂O₃: 35.73 ALZ/ La₂O₃: 21.08 La₂O₃: 42.17 Mn₂O₃ ZrO₂: 8.55 ZrO₂:17.1 Mn₂O₃: 2.5 Mn₂O₃: 5 35.73 0 NA NA Ex. 18 Al₂O₃: 18.25 Al₂O₃: 36.5ALZ/ La₂O₃: 21.52 La₂O₃: 43.04 Fe₂O₃ ZrO₂: 8.73 ZrO₂: 17.46 Fe₂O₃: 1.5Fe₂O₃: 3 NA 36.5 0 NA Ex. 19 Al₂O₃: 18.25 Al₂O₃: 36.5 ALZ/ La₂O₃: 21.52La₂O₃: 43.04 Cr₂O₃ ZrO₂: 8.73 ZrO₂: 17.46 Cr₂O₃: 1.5 Cr₂O₃: 3 36.5 0 NANA *NA = Not available

TABLE 4 Raw Material Source Alumina particles (Al₂O₃) Obtained fromAlcoa Industrial Chemicals, Bauxite, AR, under the trade designation“Al6SG” Aluminum particles (Al) Obtained from Alfa Aesar, Ward Hill, MALanthanum oxide particles (La₂O₃) Obtained from Molycorp Inc., MountainPass, CA and calcined at 700° C. for 6 hours prior to batch mixingTitanium oxide particles (TiO₂) Obtained from Kemira, Savannah, GA,under the trade designation “UNITANE 0-110” Zirconium oxide particles(ZrO₂) Obtained from Zirconia Sales, Inc. of Marietta, GA under thetrade designation “DK-2” Phosphorous oxide particles (P₂O₅) Obtainedfrom Aldrich Chemical Co., Milwaukee, WI Niobium oxide particles (Nb₂O₅)Obtained from Aldrich Chemical Co. Tantalum oxide particles (Ta₂O₅)Obtained from Aldrich Chemical Co. Strontium oxide particles (SrO)Obtained from Aldrich Chemical Co. Manganese oxide particles (Mn₂O₃)Obtained from Aldrich Chemical Co. Iron oxide particles (Fe₂O₃) Obtainedfrom Aldrich Chemical Co. Chromium oxide particles (Cr₂O₃) Obtained fromAldrich Chemical Co.

Examples 20–21

A 250-ml polyethylene bottle (7.3-cm diameter) was charged with 19.3grams of alumina particles (obtained from Alcoa Industrial Chemicals,Bauxite, Ark., under the trade designation “A16SG”), 9.5 grams ofzirconium oxide particles (obtained from Zirconia Sales, Inc. ofMarietta, Ga. under the trade designation “DK-2”), and 21.2 grams oflanthanum oxide particles (obtained from Molycorp Inc., Mountain Pass,Calif.), 75 grams of isopropyl alcohol, and 200 grams of alumina millingmedia (cylindrical shape, both height and diameter of 0.635 cm; 99.9%alumina; obtained from Coors, Golden, Colo.). The contents of thepolyethylene bottle were milled for 16 hours at 60 revolutions perminute (rpm). After the milling, the milling media were removed and theslurry was poured onto a warm (approximately 75° C.) glass (“PYREX”)pan, where it dried within 3 minutes. The dried mixture was screenedthrough a 14-mesh screen (1400 micrometer opening size) with the aid ofa paint brush and pre-sintered at 1400° C., in air, for two hours.

A hole (approximately 13 mm in diameter, about 8 cm deep) was bored atthe end of a graphite rod (approximately 60 cm long, 15 mm in diameter).About 20 grams of pre-sintered particles were inserted into the hollowend. The hollow end of the graphite rod was inserted into the hot zoneof a resistively heated furnace (obtained from Astro Industries, SantaBarbara, Calif.). The furnace was modified to convert it into a tubefurnace with graphite tube with an inner diameter of approximately 18mm. The hot zone was maintained at a temperature of 2000° C. and thefurnace was tilted approximately 30° so that the melt would not spillout of the rod. The hallow end of the rod was held in the hot zone for10 minutes to ensure uniform melting. After the ten minutes, the rod wasquickly removed from the furnace and tilted to pour the melt onto aquenching surface.

For Example 20, the quenching surface was two opposing stainless steelplates. The plates, 17.8 cm×5 cm×2.5 cm, were placed on their long edgesparallel to each other with a gap of about 1 mm. The melt was pouredinto the gap where it rapidly solidified into a plate with a z dimension(thickness) of about 1 mm. The quenched melt was predominantlytransparent and amorphous and exhibited a glass transition (T_(g)) of885° C. and a crystallization temperature (T_(x)) of 930° C. asdetermine by a DTA trace obtained as described in Example 1.

For Example 21, the quenching surface was two counter-rotating steelrollers. Rollers were 5 cm in diameter and driven by an electric motorat 80 rpm. The gap between the rollers was approximately 0.8 mm. Themelt was poured into the gap where the rollers rapidly solidified into aplate with significant x and y dimensions and a z dimension (thickness)of 0.8 mm. The quenched melt was predominantly transparent and amorphousand exhibited a glass transition (T_(g)) of 885° C. and acrystallization temperature (T_(x)) of 930° C., as determine by a DTAtrace obtained as described in Example 1.

Example 22

A polyethylene bottle was charged with 27.5 grams of alumina particles(obtained under the trade designation “APA-0.5” from Condea Vista,Tucson, Ariz.), 22.5 grams of calcium oxide particles (obtained fromAlfa Aesar, Ward Hill, Mass.) and 90 grams of isopropyl alcohol. About200 grams of zirconia milling media (obtained from Tosoh Ceramics,Division of Bound Brook, N.J., under “YTZ” designation) were added tothe bottle, and the mixture was milled at 120 revolutions per minute(rpm) for 24 hours. After the milling, the milling media were removedand the slurry was poured onto a glass (“PYREX”) pan where it was driedusing a heat-gun. The dried mixture was ground with a mortar and pestleand screened through a 70-mesh screen (212-micrometer opening size).

After grinding and screening, some of the particles were fed into ahydrogen/oxygen torch flame. The torch used to melt the particles,thereby generating melted glass beads, was a Bethlehem bench burner PM2Dmodel B, obtained from Bethlehem Apparatus Co., Hellertown, Pa.,delivering hydrogen and oxygen at the following rates. For the innerring, the hydrogen flow rate was 8 standard liters per minute (SLPM) andthe oxygen flow rate was 3 SLPM. For the outer ring, the hydrogen flowrate was 23 (SLPM) and the oxygen flow rate was 9.8 SLPM. The dried andsized particles were fed directly into the torch flame, where they weremelted and transported to an inclined stainless steel surface(approximately 51 centimeters (cm) (20 inches) wide with the slope angleof 45 degrees) with cold water running over (approximately 8liters/minute) the surface to form amorphous beads.

Examples 23 and 24

Examples 23–24 glass beads were prepared as described in Example 22,except the raw materials and the amounts of raw materials used arelisted in Table 5, below, and the milling of the raw materials wascarried out in 90 (milliliters) ml of isopropyl alcohol with 200 gramsof the zirconia media (obtained from Tosoh Ceramics, Division of BoundBrook, N.J., under “YTZ” designation) at 120 rpm for 24 hours. Thesources of the raw materials used are listed in Table 6, below.

TABLE 5 Example Weight percent of components Batch amounts, g 23 CaO: 36CaO: 18 Al₂O₃: 44 Al₂O₃: 22 ZrO₂: 20 ZrO₂: 10 24 La₂O₃: 40.9 La₂O₃:20.45 Al₂O₃: 40.98 Al₂O₃: 20.49 ZrO₂: 18.12 ZrO₂: 9.06

TABLE 6 Raw Material Source Alumina particles (Al₂O₃) Obtained fromCondea Vista, Tucson, AZ under the trade designation “APA-0.5” Calciumoxide particles (CaO) Obtained from Alfa Aesar, Ward Hill, MA Lanthanumoxide particles Obtained from Molycorp Inc. (La₂O₃) Yttria-stabilizedzirconium Obtained from Zirconia Sales, Inc. of oxide particles (Y-PSZ)Marietta, GA under the trade designation “HSY-3”

Various properties/characteristics of some of Examples 22–24 materialswere measured as follows. Powder X-ray diffraction (using an X-raydiffractometer (obtained under the trade designation “PHILLIPS XRG 3100”from PHILLIPS, Mahwah, N.J.) with copper K α1 radiation of 1.54050Angstrom)) was used to qualitatively measure phases present in examplematerials. The presence of a broad diffused intensity peak was taken asan indication of the amorphous nature of a material. The existence ofboth a broad peak and well-defined peaks was taken as an indication ofexistence of crystalline matter within an amorphous matrix. Phasesdetected in various examples are reported in Table 7, below.

TABLE 7 Phases detected via Hot-pressing Example X-ray diffraction ColorT_(g), ° C. T_(x), ° C. temp, ° C. 22 Amorphous* Clear 850 987 985 23Amorphous* Clear 851 977 975 24 Amorphous* Clear 839 932 965 *glass, asthe example has a T_(g)

For differential thermal analysis (DTA), a material was screened toretain glass beads within the 90–125 micrometer size range. DTA runswere made (using an instrument obtained from Netzsch Instruments, Selb,Germany under the trade designation “NETZSCH STA 409 DTA/TGA”). Theamount of each screened sample placed in a 100-microliter Al₂O₃ sampleholder was 400 milligrams. Each sample was heated in static air at arate of 10° C./minute from room temperature (about 25° C.) to 1200° C.

Referring to FIG. 6, line 345 is the plotted DTA data for the Example 22material. Referring to FIG. 6 line 345, the material exhibited anendothermic event at a temperature around 799° C., as evidenced by thedownward curve of line 375. It was believed that this event was due tothe glass transition (T_(g)) of the material. At about 875° C., anexothermic event was observed as evidenced by the sharp peak in line345. It was believed that this event was due to the crystallization(T_(x)) of the material. These T_(g) and T_(x) values for other examplesare reported in Table 7, above.

FIGS. 7–8 are the plotted DTA data for Examples 23 and 24, respectively.

For each of Examples 22–24, about 25 grams of the glass beads wereplaced in a graphite die and hot-pressed using uniaxial pressingapparatus (obtained under the trade designation “HP-50”, ThermalTechnology Inc., Brea, Calif.). The hot-pressing was carried out in anargon atmosphere and 13.8 megapascals (MPa) (2000 pounds per square inch(2 ksi)) pressure. The hot-pressing temperature at which appreciableglass flow occurred, as indicated by the displacement control unit ofthe hot pressing equipment described above, are reported for Examples22–24 in Table 7, above.

Examples 25–31

A polyethylene bottle was charged with the raw materials listed in Table8, below (with the sources of the raw materials listed in Table 9,below), with 90 ml of isopropyl alcohol. About 200 grams of the zirconiamilling media (obtained from Tosoh Ceramics, Division of Bound Brook,N.J., under the trade designation “YTZ”) were added to the bottle, andthe mixture was milled at 120 revolutions per minute (rpm) for 24 hours.After the milling, the milling media were removed and the slurry waspoured onto a glass (“PYREX”) pan where it was dried using a heat-gun.The dried mixture was ground with a mortar and pestle and screenedthrough a 70-mesh screen (212-micrometer opening size screen). Aftergrinding and screening, some of the particles were fed into ahydrogen/oxygen torch flame to form beads as described in Example 1.

TABLE 8 Example Weight percent of components Batch amounts, g 25 Y₂O₃:28.08 Y₂O₃: 14.04 Al₂O₃: 58.48 Al₂O₃: 29.24 ZrO₂: 13.43 ZrO₂: 6.72 26Y₂O₃: 19 Y₂O₃: 9.5 Al₂O₃: 51 Al₂O₃: 25.5 ZrO₂: 17.9 ZrO₂: 8.95 La₂O₃:12.1 La₂O₃: 6.05 27 Y₂O₃: 19.3 Y₂O₃: 9.65 Al₂O₃: 50.5 Al₂O₃: 25.25 ZrO₂:17.8 ZrO₂: 8.9 Nd₂O₃: 12.4 Nd₂O₃: 6.2 28 Y₂O₃: 27.4 Y₂O₃: 13.7 Al₂O₃:50.3 Al₂O₃: 25.15 ZrO₂: 17.8 ZrO₂: 8.9 Li₂CO₃: 4.5 Li₂CO₃: 2.25 29 Y₂O₃:27.4 Y₂O₃: 13.7 Al₂O₃: 50.3 Al₂O₃: 25.15 ZrO₂: 17.8 ZrO₂: 8.9 CaO: 4.5CaO: 2.25 30 Y₂O₃: 27.4 Y₂O₃: 13.7 Al₂O₃: 50.3 Al₂O₃: 25.15 ZrO₂: 17.8ZrO₂: 8.9 NaHCO₃: 2.25 NaHCO₃: 2.25 31 Y₂O₃: 27.4 Y₂O₃: 13.7 Al₂O₃: 50.3Al₂O₃: 25.15 ZrO₂: 17.8 ZrO₂: 8.9 SiO₂: 2.25 SiO₂: 2.25

TABLE 9 Raw Material Source Alumina particles (Al₂O₃) Obtained fromCondea Vista, Tucson, AZ under the trade designation “APA-0.5” Calciumoxide particles (CaO) Obtained from Alfa Aesar, Ward Hill, MA Lanthanumoxide particles Obtained from Molycorp Inc., Mountain (La₂O₃) Pass, CALithium carbonate particles Obtained from Aldrich Chemical Co. (Li₂CO₃)Neodymium oxide particles Obtained from Molycorp Inc. (Nd₂O₃) Silicaparticles (SiO₂) Obtained from Alfa Aesar Sodium bicarbonate particlesObtained from Aldrich Chemical Co. (NaHCO₃) Yttria-stabilized zirconiumObtained from Zirconia Sales, Inc. of oxide particles (Y-PSZ) Marietta,GA under the trade designation “HSY-3”

Various properties/characteristics of some Example 25–31 materials weremeasured as follows. Powder X-ray diffraction (using an X-raydiffractometer (obtained under the trade designation “PHILLIPS XRG 3100”from Phillips, Mahwah, N.J.) with copper K<1 radiation of 1.54050Angstrom) was used to qualitatively measure phases present in examplematerials. The presence of a broad diffused intensity peak was taken asan indication of the amorphous nature of a material. The existence ofboth a broad peak and well-defined peaks was taken as an indication ofexistence of crystalline matter within an amorphous matrix. Phasesdetected in various examples are reported in Table 10, below.

TABLE 10 Phases Hot- Exam- detected via pressing ple X-ray diffractionColor T_(g), ° C. T_(x), ° C. temp, ° C. 25 Amorphous* and Clear/milky874 932 980 Crystalline 26 Amorphous* Clear 843 938 970 27 Amorphous*Blue/pink 848 934 970 28 Amorphous* Clear 821 927 970 29 Amorphous*Clear 845 922 970 30 Amorphous* Clear 831 916 970 31 Amorphous* Clear826 926 970

For differential thermal analysis (DTA), a material was screened toretain beads in the 90–125 micrometer size range. DTA runs were made(using an instrument obtained from Netzsch Instruments, Selb, Germanyunder the trade designation “NETZSCH STA 409 DTA/TGA”). The amount ofeach screened sample placed in a 100-microliter Al₂O₃ sample holder was400 milligrams. Each sample was heated in static air at a rate of 10°C./minute from room temperature (about 25° C.) to 1200° C.

The hot-pressing temperature at which appreciable glass flow occurred,as indicated by the displacement control unit of the hot pressingequipment described above, are reported for various examples in Table10, above.

Example 32

A polyurethane-lined mill was charged with 819.6 grams of aluminaparticles (“APA-0.5”), 818 grams of lanthanum oxide particles (obtainedfrom Molycorp, Inc.), 362.4 grams of yttria-stabilized zirconium oxideparticles (with a nominal composition of 94.6 wt-% ZrO₂ (+HfO₂) and 5.4wt-% Y₂O₃; obtained under the trade designation “HSY-3” from ZirconiaSales, Inc. of Marietta, Ga.), 1050 grams of distilled water and about2000 grams of zirconia milling media (obtained from Tosoh Ceramics,Division of Bound Brook, N.J., under the trade designation “YTZ”). Themixture was milled at 120 revolutions per minute (rpm) for 4 hours tothoroughly mix the ingredients. After the milling, the milling mediawere removed and the slurry was poured onto a glass (“PYREX”) pan whereit was dried using a heat-gun. The dried mixture was ground with amortar and pestle and screened through a 70-mesh screen (212-micrometeropening size). After grinding and screening, some of the particles werefed into a hydrogen/oxygen torch flame as described in Example 1.

About 50 grams of the beads was placed in a graphite die and hot-pressedusing a uniaxial pressing apparatus (obtained under the tradedesignation “HP-50”, Thermal Technology Inc., Brea, Calif.). Thehot-pressing was carried out at 960° C. in an argon atmosphere and 13.8megapascals (MPa) (2000 pounds per square inch (2 ksi)) pressure. Theresulting translucent disk was about 48 millimeters in diameter, andabout 5 mm thick. Additional hot-press runs were performed to makeadditional disks. FIG. 9 is an optical photomicrograph of a sectionedbar (2-mm thick) of the hot-pressed material demonstrating itstransparency.

The density of the resulting hot-pressed glass material was measuredusing Archimedes method, and found to be within a range of about 4.1–4.4g/cm³. The Youngs' modulus (E) of the resulting hot-pressed glassmaterial was measured using a ultrasonic test system (obtained fromNortek, Richland, Wash. under the trade designation “NDT-140”), andfound to be within a range of about 130–150 GPa.

The average microhardnesses of the resulting hot-pressed material wasdetermined as follows. Pieces of the hot-pressed material (about 2–5millimiters in size) were mounted in mounting resin (obtained under thetrade designation “EPOMET” from Buehler Ltd., Lake Bluff, Ill.). Theresulting cylinder of resin was about 2.5 cm (1 inch) in diameter andabout 1.9 cm (0.75 inch) tall (i.e., high). The mounted samples werepolished using a conventional grinder/polisher (obtained under the tradedesignation “EPOMET” from Buehler Ltd.) and conventional diamondslurries with the final polishing step using a 1-micrometer diamondslurry (obtained under the trade designation “METADI” from Buehler Ltd.)to obtain polished cross-sections of the sample.

The microhardness measurements were made using a conventionalmicrohardness tester (obtained under the trade designation “MITUTOYOMVK-VL” from Mitutoyo Corporation, Tokyo, Japan) fitted with a Vickersindenter using a 500-gram indent load. The microhardness measurementswere made according to the guidelines stated in ASTM Test Method E384Test Methods for Microhardness of Materials (1991), the disclosure ofwhich is incorporated herein by reference. The microhardness values werean average of 20 measurements. The average microhardness of thehot-pressed material was about 8.3 GPa.

The average indentation toughness of the hot-pressed material wascalculated by measuring the crack lengths extending from the apices ofthe vickers indents made using a 500 gram load with a microhardnesstester (obtained under the trade designation “MITUTOYO MVK-VL” fromMitutoyo Corporation, Tokyo, Japan). Indentation toughness (K_(IC)) wascalculated according to the equation:K _(IC)=0.016(E/H)^(1/2)(P/c)^(3/2)wherein:E=Young's Modulus of the material;

-   -   H=Vickers hardness;    -   P=Newtons of force on the indenter;    -   c=Length of the crack from the center of the indent to its end.

Samples for the toughness were prepared as described above for themicrohardness test. The reported indentation toughness values are anaverage of 5 measurements. Crack (c) were measured with a digitalcaliper on photomicrographs taken using a scanning electron microscope(“JEOL SEM” (Model JSM 6400)). The average indentation toughness of thehot-pressed material was 1.4 MPa·m^(1/2). The thermal expansioncoefficient of the hot-pressed material was measured using a thermalanalyser (obtained from Perkin Elmer, Shelton, Conn., under the tradedesignation “PERKIN ELMER THERMAL ANALYSER”). The average thermalexpansion coefficient was 7.6×10⁻⁶/° C.

The thermal conductivity of the hot-pressed material was measuredaccording to an ASTM standard “D 5470-95, Test Method A” (1995), thedisclosure of which is incorporated herein by reference. The averagethermal conductivity was 1.15 W/m*K.

The translucent disk of hot-pressed La₂O₃—Al₂O₃—ZrO₂ glass washeat-treated in a furnace (an electrically heated furnace (obtainedunder the trade designation “Model KKSK-666-3100” from Keith Furnaces ofPico Rivera, Calif.)) as follows. The disk was first heated from roomtemperature (about 25° C.) to about 900° C. at a rate of about 10°C./min and then held at 900° C. for about 1 hour. Next, the disk washeated from about 900° C. to about 1300° C. at a rate of about 10°C./min and then held at 1300° C. for about 1 hour, before cooling backto room temperature by turning off the furnace. Additional runs wereperformed with the same heat-treatment schedule to make additionaldisks.

FIG. 10 is a scanning electron microscope (SEM) photomicrograph of apolished section of heat-treated Example 32 material showing the finecrystalline nature of the material. The polished section was preparedusing conventional mounting and polishing techniques. Polishing was doneusing a polisher (obtained from Buehler of Lake Bluff, Ill. under thetrade designation “ECOMET 3 TYPE POLISHER-GRINDER”). The sample waspolished for about 3 minutes with a diamond wheel, followed by threeminutes of polishing with each of 45, 30, 15, 9, and 3-micrometerdiamond slurries. The polished sample was coated with a thin layer ofgold-palladium and viewed using JEOL SEM (Model JSM 840A).

Based on powder X-ray diffraction of a portion of heat-treated Example32 material and examination of the polished sample using SEM in thebackscattered mode, it is believed that the dark portions in thephotomicrograph were crystalline LaAl₁₁O_(18,) the gray portionscrystalline LaAlO₃, and the white portions crystalline cubic/tetragonalZrO₂.

The density of the heat-treated material was measured using Archimedesmethod, and found to be about 5.18 g/cm³. The Youngs' modulus (E) of theheat-treated material was measured using an ultrasonic test system(obtained from Nortek, Richland, Wash. under the trade designation“NDT-140”), and found to be about 260 GPa. The average microhardness ofthe heat-treated material was determined as described above for theExample 32 glass beads, and was found to be 18.3 GPa. The averagefracture toughness (K_(IC)) of the heat-treated material was determinedas described above for the Example 32 hot-pressed material, and wasfound to be 3.3 MPa*m^(1/2).

Examples 33–49

Examples 33–49 beads were prepared as described in Example 32, exceptthe raw materials and the amounts of raw materials, used are listed inTable 11, below, and the milling of the raw materials was carried out in90 milliliters (ml) of isopropyl alcohol with 200 grams of the zirconiamedia (obtained from Tosoh Ceramics, Division of Bound Brook, N.J.,under the trade designation “YTZ”) at 120 rpm for 24 hours. The sourcesof the raw materials used are listed in Table 12, below.

TABLE 11 Weight percent of Example components Batch amounts, g 33 La₂O₃:45.06 La₂O₃: 22.53 Al₂O₃: 34.98 Al₂O₃: 17.49 ZrO₂: 19.96 ZrO₂: 9.98 34La₂O₃: 36.74 La₂O₃: 18.37 Al₂O₃: 46.98 Al₂O₃: 23.49 ZrO₂: 16.28 ZrO₂:8.14 35 La₂O₃: 35.35 La₂O₃: 17.68 Al₂O₃: 48.98 Al₂O₃: 24.49 ZrO₂: 15.66ZrO₂: 7.83 36 Al₂O₃: 41.0 Al₂O₃: 20.5 ZrO₂: 17.0 ZrO₂: 8.5 Eu₂O₃: 41.0Eu₂O₃: 20.5 37 Al₂O₃: 41.0 Al₂O₃: 20.5 ZrO₂: 18.0 ZrO₂: 9.0 Gd₂O₃: 41.0Gd₂O₃: 20.5 38 Al₂O₃: 41.0 Al₂O₃: 20.5 ZrO₂: 18.0 ZrO₂: 9.0 Dy₂O₃: 41.0Dy₂O₃: 20.5 39 La₂O₃: 35.0 La₂O₃: 17.5 Al₂O₃: 40.98 Al₂O₃: 20.49 ZrO₂:18.12 ZrO₂: 9.06 Nd₂O₃: 5.0 Nd₂O₃: 2.50 40 La₂O₃: 35.0 La₂O₃: 17.5Al₂O₃: 40.98 Al₂O₃: 20.49 ZrO₂: 18.12 ZrO₂: 9.06 CeO₂: 5.0 CeO₂: 2.50 41HfO₂: 35.5 HfO₂: 17.75 Al₂O₃: 32.5 Al₂O₃: 16.25 La₂O₃: 32.5 La₂O₃: 16.2542 La₂O₃: 41.7 La₂O₃: 20.85 Al₂O₃: 35.4 Al₂O₃: 17.7 ZrO₂: 16.9 ZrO₂:8.45 MgO: 6.0 MgO: 3.0 43 La₂O₃: 43.02 La₂O₃: 21.51 Al₂O₃: 36.5 Al₂O₃:18.25 ZrO₂: 17.46 ZrO₂: 8.73 Li₂CO₃: 3.0 Li₂CO₃: 1.50 44 La₂O₃: 41.7La₂O₃: 20.85 Al₂O₃: 35.4 Al₂O₃: 17.70 ZrO₂: 16.9 ZrO₂: 8.45 Li₂CO₃: 6.0Li₂CO₃: 3.00 45 La₂O₃: 38.8 La₂O₃: 19.4 Al₂O₃: 40.7 Al₂O₃: 20.35 ZrO₂:17.5 ZrO₂: 8.75 Li₂CO₃: 3 Li₂CO₃: 1.50 46 La₂O₃: 43.02 La₂O₃: 21.51Al₂O₃: 36.5 Al₂O₃: 18.25 ZrO₂: 17.46 ZrO₂: 8.73 TiO₂: 3 TiO₂: 1.50 47La₂O₃: 43.02 La₂O₃: 21.51 Al₂O₃: 36.5 Al₂O₃: 18.25 ZrO₂: 17.46 ZrO₂:8.73 NaHCO₃: 3.0 NaHCO₃: 1.50 48 La₂O₃: 42.36 La₂O₃: 21.18 Al₂O₃: 35.94Al₂O₃: 17.97 ZrO₂: 17.19 ZrO₂: 8.60 NaHCO₃: 4.5 NaHCO₃: 2.25 49 La₂O₃:43.02 La₂O₃: 21.51 Al₂O₃: 36.5 Al₂O₃: 18.25 ZrO₂: 17.46 ZrO₂: 8.73 MgO:1.5 MgO: 0.75 NaHCO₃: 1.5 NaHCO₃: 0.75 TiO₂: 1.5 TiO₂: 0.75

TABLE 12 Raw Material Source Alumina particles (Al₂O₃) Obtained fromCondea Vista, Tucson, AZ under the trade designation “APA-0.5” Ceriumoxide particles (CeO₂) Obtained from Rhone-Poulenc, France Europiumoxide particles (Eu₂O₃) Obtained from Aldrich Chemical Co. Gadoliniumoxide particles (Gd₂O₃) Obtained from Molycorp Inc., Mountain Pass, CAHafnium oxide particles (HfO₂) Obtained from Teledyne Wah Chang AlbanyCo., Albany, OR Lanthanum oxide particles (La₂O₃) Obtained from MolycorpInc. Lithium carbonate particles (Li₂CO₃) Obtained from Aldrich ChemicalCo. Magnesium oxide particles (MgO) Obtained from Aldrich Chemical Co.Neodymium oxide particles (Nd₂O₃) Obtained from Molycorp Inc. Sodiumbicarbonate particles (NaHCO₃) Obtained from Aldrich Chemical Co.Titanium dioxide particles (TiO₂) Obtained from Kemira Inc., Savannah,GA Yttria-stabilized zirconium oxide particles Obtained from ZirconiaSales, Inc. of (Y-PSZ) Marietta, GA under the trade designation “HSY-3”

Various properties/characteristics of some Example 32–49 materials weremeasured as follows. Powder X-ray diffraction (using an X-raydiffractometer (obtained under the trade designation “PHILLIPS XRG 3100”from PHILLIPS, Mahwah, N.J.) with copper K α1 radiation of 1.54050Angstrom)) was used to qualitatively measure phases present in examplematerials. The presence of a broad diffused intensity peak was taken asan indication of the glassy nature of a material. The existence of botha broad peak and well-defined peaks was taken as an indication ofexistence of crystalline matter within a glassy matrix. Phases detectedin various examples are reported in Table 13, below.

TABLE 13 Phases detected Hot- via X-ray pressing Example diffractionColor T_(g), ° C. T_(x), ° C. temp, ° C. 32 Amorphous* Clear 834 932 96033 Amorphous* Clear 837 936 960 34 Amorphous* Clear 848 920 960 35Amorphous* Clear 856 918 960 36 Amorphous* Intense 874 921 975 yellow/mustard 37 Amorphous* Clear 886 933 985 38 Amorphous* Greenish 881 935985 39 Amorphous* Blue/pink 836 930 965 40 Amorphous* Yellow 831 934 96541 Amorphous* Light green 828 937 960 42 Amorphous* Clear 795 901 950 43Amorphous* Clear 816 942 950 44 Amorphous* Clear 809 934 950 45Amorphous* Clear/ 840 922 950 greenish 46 Amorphous* Clear 836 934 95047 Amorphous* Clear 832 943 950 48 Amorphous* Clear 830 943 950 49Amorphous* Clear/some 818 931 950 green *glass, as the example has aT_(g)

For differential thermal analysis (DTA), a material was screened toretain beads in the 90–125 micrometer size range. DTA runs were made(using an instrument obtained for Netzsch Instruments, Selb, Germanyunder the trade designation “NETZSCH STA 409 DTA/TGA”). The amount ofeach screened sample placed in a 100-microliter Al₂O₃ sample holder was400 milligrams. Each sample was heated in static air at a rate of 10°C./minute from room temperature (about 25° C.) to 1200° C.

Referring to FIG. 11, line 801 is the plotted DTA data for the Example32 material. Referring to FIG. 11 line 801, the material exhibited anendothermic event at temperature around 840° C., as evidenced by thedownward curve of line 801. It was believed that this event was due tothe glass transition (T_(g)) of the material. At about 934° C., anexothermic event was observed as evidenced by the sharp peak in line801. It was believed that this event was due to the crystallization(T_(x)) of the material. These T_(g) and T_(x) values for other examplesare reported in Table 13, above.

The hot-pressing temperature at which appreciable glass flow occurred,as indicated by the displacement control unit of the hot pressingequipment described above, are reported for various examples in Table13, above.

Example 50

A polyethylene bottle was charged with 20.49 grams of alumina particles(“APA-0.5”), 20.45 grams of lanthanum oxide particles (obtained fromMolycorp, Inc.), 9.06 grams of yttria-stabilized zirconium oxideparticles (with a nominal composition of 94.6 wt-% ZrO₂ (+HfO₂) and 5.4wt-% Y₂O₃; obtained under the trade designation “HSY-3” from ZirconiaSales, Inc. of Marietta, Ga.), and 80 grams of distilled water. About450 grams of alumina milling media (10 mm diameter; 99.9% alumina;obtained from Union Process, Akron, Ohio) were added to the bottle, andthe mixture was milled at 120 revolutions per minute (rpm) for 4 hoursto thoroughly mix the ingredients. After the milling, the milling mediawere removed and the slurry was poured onto a glass (“PYREX”) pan whereit was dried using a heat-gun. The dried mixture was ground with amortar and pestle and screened through a 70-mesh screen (212-micrometeropening size).

A small quantity of the dried particles was melted in an arc dischargefurnace (Model No. 5T/A 39420; from Centorr Vacuum Industries, Nashua,N.H.). About 1 gram of the dried and sized particles was placed on achilled copper plate located inside the furnace chamber. The furnacechamber was evacuated and then backfilled with Argon gas at 13.8kilopascals (kPa) (2 pounds per square inch (psi)) pressure. An arc wasstruck between an electrode and a plate. The temperatures generated bythe arc discharge were high enough to quickly melt the dried and sizedparticles. After melting was complete, the material was maintained in amolten state for about 10 seconds to homogenize the melt. The resultantmelt was rapidly cooled by shutting off the arc and allowing the melt tocool on its own. Rapid cooling was ensured by the small mass of thesample and the large heat sinking capability of the water chilled copperplate. The fused material was removed from the furnace within one minuteafter the power to the furnace was turned off. Although not wanting tobe bound by theory, it is estimated that the cooling rate of the melt onthe surface of the water chilled copper plate was above 100° C./second.The fused material were transparent glass beads (largest diameter of abead was measured at 2.8 millimeters (mm)).

The resulting amorphous beads were placed in a poyethylene bottle (as inExample 1) together with 200 grams of 2-mm zirconia milling media(obtained from Tosoh Ceramics Bound Brook, N.J. under the tradedesignation “YTZ”). Three hundred grams of distilled water was added tothe bottle, and the mixture milled for 24 hours at 120 rpm to pulverizebeads into powder. The milled material was dried using a heat gun.Fifteen grams of the dried particles were placed in a graphite die andhot-pressed at 960° C. as described in Examples 5–7. The resulting diskwas translucent.

Example 51

Example 51 fused amorphous beads were prepared as described in Example50. About 15 grams of the beads were hot pressed as described in Example50 except the bottom punch of the graphite die had 2 mm deep grooves.The resulting material replicated the grooves, indicating very goodflowability of the glass during the heating under the applied pressure.

Comparative Example A

Comparative Example A fused material was prepared as described inExample 50, except the polyethylene bottle was charged with 27 grams ofalumina particles (“APA-0.5”), 23 grams of yttria-stabilized zirconiumoxide particles (with a nominal composition of 94.6 wt-% ZrO₂ (+HfO₂)and 5.4 wt-% Y₂O₃; obtained under the trade designation “HSY-3” fromZirconia Sales, Inc. of Marietta, Ga.) and 80 grams of distilled water.The composition of this example corresponds to a eutectic composition inthe Al₂O₃—ZrO₂ binary system. The resulting 100–150 micrometers diameterspheres were partially amorphous, with significant portions ofcrystallinity as evidenced by X-ray diffraction analysis.

Example 52

A sample (31.25 grams) of amorphous beads prepared as described inExample 32, and 18.75 grams of beads prepared as described inComparative Example A, were placed in a polyethylene bottle. After 80grams of distilled water and 300 grams of zirconia milling media (TosohCeramics, Bound Brook, N.J. under the trade designation “YTZ”) wereadded to the bottle, the mixture was milled for 24 hours at 120 rpm. Themilled material was dried using a heat gun. Twenty grams of the driedparticles were hot-pressed as described in Example 32. An SEMphotomicrograph of a polished section prepared as described in Example32 of Example 32 material is shown in FIG. 12. The absence of crackingat interfaces between the Comparative Example A material (dark areas)and the Example 52 material (light areas) indicates the establishment ofgood bonding.

Grinding Performance of Examples 32 and 32A and Comparative Examples B–D

Example 32 hot-pressed material was crushed by using a “Chipmunk” jawcrusher (Type VD, manufactured by BICO Inc., Burbank, Calif.) into(abrasive) particles and graded to retain the −25+30 mesh fraction(i.e., the fraction collected between 25-micrometer opening and30-micrometer opening size sieves) and −30+35 mesh fractions (i.e., thefraction collected between 30-micrometer opening size and 35-micrometeropening size sieves) (USA Standard Testing Sieves). These two meshfractions were combined to provide a 50/50 blend. The blended materialwas heat treated as described in Example 32. Thirty grams of theresulting glass-ceramic abrasive particles were incorporated into acoated abrasive disc. The coated abrasive disc was made according toconventional procedures. The glass-ceramic abrasive particles werebonded to 17.8 cm diameter, 0.8 mm thick vulcanized fiber backings(having a 2.2 cm diameter center hole) using a conventional calciumcarbonate-filled phenolic make resin (48% resole phenolic resin, 52%calcium carbonate, diluted to 81% solids with water and glycol ether)and a conventional cryolite-filled phenolic size resin (32% resolephenolic resin, 2% iron oxide,

-   66% cryolite, diluted to 78% solids with water and glycol ether).    The wet make resin weight was about 185 g/m². Immediately after the    make coat was applied, the glass-ceramic abrasive particles were    electrostatically coated. The make resin was precured for 120    minutes at 88° C. Then the cryolite-filled phenolic size coat was    coated over the make coat and abrasive particles. The wet size    weight was about 850 g/m². The size resin was cured for 12 hours at    99° C. The coated abrasive disc was flexed prior to testing.

Example 32A coated abrasive disk was prepared as described for Example32 except the Example 32A abrasive particles were obtained by crushing ahot-pressed and heat-treated Example 32 material, rather than crushingthen heat-treating.

Comparative Example B coated abrasive disks were prepared as describedfor Example 32 (above), except heat-treated fused alumina abrasiveparticles (obtained under the trade designation “ALODUR BFRPL”” fromTriebacher, Villach, Austria) was used in place of the Example 32glass-ceramic abrasive particles.

Comparative Example C coated abrasive discs were prepared as describedfor Example 32 (above), except alumina-zirconia abrasive particles(having a eutectic composition of 53% Al₂O₃ and 47% ZrO₂; obtained underthe trade designation “NORZON” from Norton Company, Worcester, Mass.)were used in place of the Example 32 glass-ceramic abrasive particles.

Comparative Example D coated abrasive discs were prepared as describedabove except sol-gel-derived abrasive particles (marketed under thetrade designation “321 CUBITRON” from the 3M Company, St. Paul, Minn.)was used in place of the Example 32 glass-ceramic abrasive particles.

The grinding performance of Example 32 and Comparative Examples B–Dcoated abrasive discs were evaluated as follows. Each coated abrasivedisc was mounted on a beveled aluminum back-up pad, and used to grindthe face of a pre-weighed 1.25 cm×18 cm×10 cm 1018 mild steel workpiece.The disc was driven at 5,000 rpm while the portion of the discoverlaying the beveled edge of the back-up pad contacted the workpieceat a load of 8.6 kilograms. Each disc was used to grind an individualworkpiece in sequence for one-minute intervals. The total cut was thesum of the amount of material removed from the workpieces throughout thetest period. The total cut by each sample after 12 minutes of grindingas well as the cut at the 12th minute (i.e., the final cut) are reportedin Table 14, below. The Example 32 results are an average of two discs,where as one disk was tested for each of Example 32A, and ComparativeExamples B, C, and D.

TABLE 14 Example Total cut, g Final cut, g 32 1163 92 32A 1197 92 Comp.B 514 28 Comp. C 689 53 Comp. D 1067 89

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

1. Amorphous material comprising Al₂O₃, ZrO₂, and a metal oxide otherthan Al₂O₃ or ZrO₂, wherein the ZrO₂ is present in an amount of at least15 precent by weight, based on the total weight of the amorphousmaterial, wherein at least a portion of the metal oxide other than Al₂O₃or ZrO₂ forms a distinct crystalline phase if the amorphous material iscrystallized, wherein the amorphous material comprises at least 50percent by weight collectively of the Al₂O₃ and the ZrO₂, based on thetotal weight of the amorphous material, wherein the amorphous materialcontains not more than 20 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theamorphous material, wherein the amorphous material has x, y, and zdimensions each perpendicular to each other, and wherein each of the x,y, and z dimensions is at least 25 micrometers.
 2. The amorphousmaterial according to claim 1 wherein the amorphous material does nothave a T_(g).
 3. The amorphous material according to claim 1 comprisingat least 35 percent by weight Al₂O₃, based on the total weight of theamorphous material.
 4. The amorphous material according to claim 1comprising Al₂O₃ in a range of about 55 to about 65 percent by weight toa range of about 45 to about 35 percent by weight ZrO₂, based on thetotal Al₂O₃ and ZrO₂ content of the amorphous material.
 5. The amorphousmaterial according to claim 1 wherein the metal oxide other than Al₂O₃or ZrO₂ is TiO₂.
 6. Ceramic comprising the amorphous material accordingto claim
 1. 7. The ceramic according to claim 6 wherein the amorphousmaterial is glass.
 8. A method for making amorphous material comprisingAl₂O₃, ZrO₂, and a metal oxide other than Al₂O₃ or ZrO₂, wherein theZrO₂ is present in an amount of at least 15 percent by weight, based onthe total weight of the amorphous material, wherein at least a portionof the metal oxide other than Al₂O₃ or ZrO₂ forms a distinct crystallinephase if the amorphous material is crystallized, wherein the amorphousmaterial comprises at least 50 percent by weight collectively of theAl₂O₃ and the ZrO₂, based on the total weight of the amorphous material,wherein the amorphous material contains not more than 20 percent byweight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, basedon the total weight of the amorphous material, wherein the amorphousmaterial has x, y, and z dimensions each perpendicular to each other,and wherein each of the x, y, and z dimensions is at least 25micrometers, the method comprising: melting sources of at least Al₂O₃,ZrO₂, and a metal oxide other than Al₂O₃ or ZrO₂ to provide a melt; andcooling the melt to provide the amorphous material.
 9. Glass-ceramiccomprising Al₂O₃, ZrO₂, and a metal oxide other than Al₂O₃ or ZrO₂,wherein at least a portion of the metal oxide other than Al₂O₃ or ZrO₂is present as at least one distinct crystalline phase, wherein theglass-ceramic comprises at least 50 percent by weight collectively ofthe Al₂O₃ and the ZrO₂, based on the total weight of the glass-ceramic,wherein the glass-ceramic contains not more than 20 percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the glass-ceramic, wherein the glass-ceramic has x, y,and z dimensions each perpendicular to each other, and wherein each ofthe x, y, and z dimensions is at least 25 micrometers.
 10. A method formaking glass-ceramic, the method comprising: heat-treating amorphousmaterial such that at least a portion of the amorphous material isconverted to a glass-ceramic, wherein the amorphous material comprisesAl₂O₃, ZrO₂, and a metal oxide other than Al₂O₃ or ZrO₂, wherein atleast a portion of the metal oxide other than Al₂O₃ or ZrO₂ forms adistinct crystalline phase during the heat-treating, wherein theamorphous material comprises at least 50 percent by weight collectivelyof the Al₂O₃ and the ZrO₂, based on the total weight of the amorphousmaterial, wherein the amorphous material contains not more than 20percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the amorphous material, wherein theamorphous material has x, y, and z dimensions each perpendicular to eachother, wherein each of the x, y, and z dimensions is at least 25micrometers, wherein the glass-ceramic comprises Al₂O₃, ZrO₂, and ametal oxide other than Al₂O₃ or ZrO₂, wherein at least a portion of themetal oxide other than Al₂O₃ or ZrO₂ is present as at least one distinctcrystalline phase, wherein the glass-ceramic comprises at least 50percent by weight collectively of the Al₂O₃ and the ZrO₂, based on thetotal weight of the glass-ceramic, wherein the glass-ceramic containsnot more than 20 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass-ceramic,wherein the glass-ceramic has x, y, and z dimensions each perpendicularto each other, and wherein each of the x, y, and z dimensions is atleast 25 micrometers.
 11. A plurality of abrasive particles having aspecified nominal grade, wherein at least a portion of the abrasiveparticles is a plurality of abrasive particles comprising aglass-ceramic, wherein the glass-ceramic comprises Al₂O₃, at least 15percent by weight ZrO₂, based on the total weight of the glass-ceramicof each particle of the portion, and Y₂O₃, wherein at least a portion ofthe Y₂O₃ is present as at least one distinct crystalline phase.
 12. Aplurality of abrasive particles having a specified nominal grade,wherein at least a portion of the abrasive particles is a plurality ofabrasive particles comprising a glass-ceramic, wherein the glass-ceramiccomprises Al₂O₃, at least 15 percent by weight ZrO₂, based on the totalweight of the glass-ceramic of each particle of the portion, and REO,wherein at least a portion of the REO is present as at least onedistinct crystalline phase.
 13. A plurality of abrasive particles havinga specified nominal grade, wherein at least a portion of the abrasiveparticles is a plurality of abrasive particles comprising aglass-ceramic, wherein the glass-ceramic comprises Al₂O₃, at least 15percent by weight ZrO₂, based on the total weight of the glass-ceramicof each particle of the portion, and contains not more than 10 percentby weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅,based on the total weight of the glass-ceramic of each particle of theportion, wherein the glass-ceramic of at least some of the portion ofabrasive particles has x, y, and z dimensions each perpendicular to eachother, and wherein each of the x, y, and z dimensions is at least 25micrometers.
 14. A plurality of abrasive particles having a specifiednominal grade, wherein at least a portion of the abrasive particles is aplurality of abrasive particles comprising a glass-ceramic, wherein theglass-ceramic comprises Al₂O₃, ZrO₂, and a metal oxide other than Al₂O₃or ZrO₂, wherein at least a portion of the metal oxide other than Al₂O₃or ZrO₂ is present as at least one distinct crystalline phase, whereinthe glass-ceramic of each particle of the portion collectively comprisesat least 50 percent by weight collectively of the Al₂O₃ and the ZrO₂,based on the total weight of the glass-ceramic of each particle of theportion, wherein the glass-ceramic of each particle of the portioncontains not more than 20 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theglass-ceramic of each particle of the portion.
 15. A method for makingabrasive particles, the method comprising: providing a plurality ofparticles having a specified nominal grade, wherein at least a portionof the particles is a plurality of particles comprising an amorphousmaterial, wherein the amorphous material comprises Al₂O₃, ZrO₂, and ametal oxide other than Al₂O₃ or ZrO₂, wherein at least a portion of themetal oxide other than Al₂O₃ or ZrO₂ forms a distinct crystalline phaseduring heat-treating, wherein the amorphous material comprises at least50 percent by weight collectively of the Al₂O₃ and the ZrO₂, based onthe total weight of the amorphous material, wherein the amorphousmaterial contains not more than 20 percent by weight collectively As₂O₃,B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, V₂O₅, based on the total weight of theamorphous material; and heat-treating the particles comprising amorphousmaterial to provide abrasive particles comprising a glass-ceramic suchthat at least a portion of the amorphous material is converted to aglass-ceramic and such that a plurality of abrasive particles having aspecified nominal grade is provided, wherein at least a portion of theabrasive particles is a plurality of the abrasive particles comprisingthe glass-ceramic, wherein the glass-ceramic comprises the Al₂O₃, theZrO₂, and the metal oxide other than Al₂O₃ or ZrO₂, wherein at least aportion of the metal oxide other than Al₂O₃ or ZrO₂ is present as atleast one distinct crystalline phase, wherein the glass-ceramic of eachparticle of the portion collectively comprises at least 50 percent byweight collectively of the Al₂O₃ and the ZrO₂, based on the total weightof the glass-ceramic of each particle of the portion, wherein theglass-ceramic of each particle of the portion contains not more than 20percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the glass-ceramic of each particle ofthe portion.
 16. A method for making abrasive particles, the methodcomprising: heat-treating particles comprising an amorphous materialsuch that at least a portion of the amorphous material is converted to aglass-ceramic, wherein the amorphous material comprises Al₂O₃, ZrO₂, anda metal oxide other than Al₂O₃ or ZrO₂, wherein at least a portion ofthe metal oxide other than Al₂O₃ or ZrO₂ forms a distinct crystallinephase during the heat-treating, wherein the amorphous material comprisesat least 50 percent by weight collectively of the Al₂O₃ and the ZrO₂,based on the total weight of the amorphous material, wherein theamorphous material contains not more than 20 percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on thetotal weight of the amorphous material, wherein the glass-ceramiccomprises the Al₂O₃, the ZrO₂, and the metal oxide other than Al₂O₃ orZrO₂, wherein at least a portion of the metal oxide other than Al₂O₃ orZrO₂ is present as at least one distinct crystalline phase, wherein theglass-ceramic of each particle of the portion collectively comprises atleast 50 percent by weight collectively of the Al₂O₃ and the ZrO₂, basedon the total weight of the glass-ceramic of each particle of theportion, wherein the glass-ceramic of each particle of the portioncontains not more than 20 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theglass-ceramic of each particle of the portion; and grading the abrasiveparticles comprising the glass-ceramic to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 17. A method for makingabrasive particles, the method comprising: heat-treating ceramiccomprising an amorphous material such that at least a portion of theamorphous material is converted to a glass-ceramic, wherein theamorphous material comprises Al₂O₃, ZrO₂, and a metal oxide other thanAl₂O₃ or ZrO₂, wherein at least a portion of the metal oxide other thanAl₂O₃ or ZrO₂ forms a distinct crystalline phase during theheat-treating, wherein the amorphous material comprises at least 50percent by weight collectively of the Al₂O₃ and the ZrO₂, based on thetotal weight of the amorphous material, wherein the amorphous materialcontains not more than 20 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theamorphous material, wherein the glass-ceramic comprises the Al₂O₃, theZrO₂, and the metal oxide other than Al₂O₃ or ZrO₂, wherein at least aportion of the metal oxide other than Al₂O₃ or ZrO₂ is present as atleast one distinct crystalline phase, wherein the glass-ceramiccomprises at least 50 percent by weight collectively of the Al₂O₃ andthe ZrO₂, based on the total weight of the glass-ceramic, wherein theglass-ceramic contains not more than 20 percent by weight collectivelyAs₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weightof the glass-ceramic; crushing the glass-ceramic to provide abrasiveparticles comprising the glass-ceramic; and grading the abrasiveparticles comprising the glass-ceramic to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 18. The methodaccording to claim 17 wherein the amorphous material has x, y, and zdimensions each perpendicular to each other, wherein each of the x, y,and z dimensions is at least 25 micrometers, and the glass-ceramic hasx, y, and z dimensions each perpendicular to each other, wherein each ofthe x, y, and z dimensions is at least 25 micrometers.
 19. A method formaking abrasive particles, the method comprising: providing a pluralityof particles having a specified nominal grade, wherein at least aportion of the particles is a plurality of particles comprising anamorphous material, wherein the amorphous material comprises Al₂O₃, atleast 15 percent by weight ZrO₂, based on the total weight of theamorphous material, and Y₂O₃, wherein at least a portion of the Y₂O₃forms a distinct crystalline phase during heat-treating; andheat-treating the particles comprising amorphous material to provideabrasive particles comprising a glass-ceramic such that at least aportion of the amorphous material is converted to a glass-ceramic andsuch that a plurality of abrasive particles having a specified nominalgrade is provided, wherein at least a portion of the abrasive particlesis a plurality of the abrasive particles comprising the glass-ceramic,wherein the glass-ceramic comprises the Al₂O₃, the at least 15 percentby weight ZrO₂, based on the total weight of the glass-ceramic of eachparticle of the portion, and the Y₂O₃, wherein at least a portion of theY₂O₃ is present as at least one distinct crystalline phase.
 20. A methodfor making abrasive particles, the method comprising: heat-treatingparticles comprising an amorphous material such that at least a portionof the amorphous material is converted to a glass-ceramic, wherein theamorphous material comprises Al₂O₃, at least 15 percent by weight ZrO₂,based on the total weight of the amorphous material, and Y₂O₃, whereinat least a portion of the Y₂O₃ forms a distinct crystalline phase duringthe heat-treating, wherein the glass-ceramic comprises the Al₂O₃, the atleast 15 percent by weight ZrO₂, based on the total weight of theamorphous material, and the Y₂O₃, wherein at least a portion of the Y₂O₃is present as at least one distinct crystalline phase; and grading theabrasive particles comprising the glass-ceramic to provide a pluralityof abrasive particles having a specified nominal grade, wherein at leasta portion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 21. A method for makingabrasive particles, the method comprising: heat-treating ceramiccomprising an amorphous material such that at least a portion of theamorphous material is converted to a glass-ceramic, wherein theamorphous material comprises Al₂O₃, at least 15 percent by weight ZrO₂,based on the total weight of the amorphous material, and Y₂O₃, whereinat least a portion of the Y₂O₃ forms a distinct crystalline phase duringthe heat-treating, wherein the glass-ceramic comprises the Al₂O₃, the atleast 15 percent by weight ZrO₂, based on the total weight of theamorphous material, and the Y₂O₃, wherein at least a portion of the Y₂O₃is present as at least one distinct crystalline phase; crushing theglass-ceramic to provide abrasive particles comprising theglass-ceramic; and grading the abrasive particles comprising theglass-ceramic to provide a plurality of abrasive particles having aspecified nominal grade, wherein at least a portion of the plurality ofabrasive particles is a plurality of the abrasive particles comprisingthe glass-ceramic.
 22. A method for making abrasive particles, themethod comprising: providing a plurality of particles having a specifiednominal grade, wherein at least a portion of the particles is aplurality of particles comprising an amorphous material, wherein theamorphous material comprises Al₂O₃, at least 15 percent by weight ZrO₂,based on the total weight of the amorphous material, and REO, wherein atleast a portion of the REO forms a distinct crystalline phase duringheat-treating; and heat-treating the particles comprising amorphousmaterial to provide abrasive particles comprising a glass-ceramic suchthat at least a portion of the amorphous material is converted to aglass-ceramic and such that a plurality of abrasive particles having aspecified nominal grade is provided, wherein at least a portion of theabrasive particles is a plurality of the abrasive particles comprisingthe glass-ceramic, wherein the glass-ceramic comprises the Al₂O₃, the atleast 15 percent by weight ZrO₂, based on the total weight of theglass-ceramic of each particle of the portion, and the REO, wherein atleast a portion of the REO is present as at least one distinctcrystalline phase.
 23. A method for making abrasive particles, themethod comprising: heat-treating particles comprising an amorphousmaterial such that at least a portion of the amorphous material isconverted to a glass-ceramic, wherein the amorphous material comprisesAl₂O₃, at least 15 percent by weight ZrO₂, based on the total weight ofthe amorphous material, and REO, wherein at least a portion of the REOforms a distinct crystalline phase during the heat-treating, wherein theglass-ceramic comprises the Al₂O₃, the at least 15 percent by weightZrO₂, based on the total weight of the amorphous material, and the REO,wherein at least a portion of the REO is present as at least onedistinct crystalline phase; and grading the abrasive particlescomprising the glass-ceramic to provide a plurality of abrasiveparticles having a specified nominal grade, wherein at least a portionof the plurality of abrasive particles is a plurality of the abrasiveparticles comprising the glass-ceramic.
 24. A method for making abrasiveparticles, the method comprising: heat-treating ceramic comprising anamorphous material such that at least a portion of the amorphousmaterial is converted to a glass-ceramic, wherein the amorphous materialcomprises Al₂O₃, at least 15 percent by weight ZrO₂, based on the totalweight of the amorphous material, and REO, wherein at least a portion ofthe REO forms a distinct crystalline phase during the heat-treating,wherein the glass-ceramic comprises the Al₂O₃, the at least 15 percentby weight ZrO₂, based on the total weight of the amorphous material, andthe REO, wherein at least a portion of the REO is present as at leastone distinct crystalline phase; crushing the glass-ceramic to provideabrasive particles comprising the glass-ceramic; and grading theabrasive particles comprising the glass-ceramic to provide a pluralityof abrasive particles having a specified nominal grade, wherein at leasta portion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 25. A method for makingabrasive particles, the method comprising: providing a plurality ofparticles having a specified nominal grade, wherein at least a portionof the particles is a plurality of particles comprising an amorphousmaterial, wherein the amorphous material comprises Al₂O₃, at least 15percent by weight ZrO₂, based on the total weight of the amorphousmaterial of each particle of the portion, and contains not more than 10percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the amorphous material of eachparticle of the portion, wherein the amorphous material of at least someof the portion of particles has x, y, and z dimensions eachperpendicular to each other, and wherein each of the x, y, and zdimensions is at least 25 micrometers; and heat-treating the particlescomprising the amorphous material to provide abrasive particlescomprising a glass-ceramic such that at least a portion of the amorphousmaterial is converted to a glass-ceramic and such that a plurality ofabrasive particles having a specified nominal grade is provided, whereinat least a portion of the abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic, wherein theglass-ceramic comprises the Al₂O₃, the at least 15 percent by weightZrO₂, based on the total weight of the glass-ceramic of each particle ofthe portion, and contains not more than 10 percent by weightcollectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, weight ofthe glass-ceramic of each particle of the portion, wherein theglass-ceramic of at least some of the portion of abrasive particles hasx, y, and z dimensions each perpendicular to each other, and whereineach of the x, y, and z dimensions is at least 25 micrometers.
 26. Amethod for making abrasive particles, the method comprising:heat-treating particles comprising an amorphous material such that atleast a portion of the amorphous material is converted to aglass-ceramic, wherein the amorphous material comprises Al₂O₃, at least15 percent by weight ZrO₂, based on the total weight of the amorphousmaterial of each particle comprising the amorphous material, andcontains not more than 10 percent by weight collectively As₂O₃, B₂O₃,GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theamorphous material of each particle comprising the amorphous material,wherein the amorphous material of at least some of the particles has x,y, and z dimensions each perpendicular to each other, and wherein eachof the x, y, and z dimensions is at least 25 micrometers, wherein theglass-ceramic comprises the Al₂O₃, the at least 15 percent by weightZrO₂, based on the total weight of the glass-ceramic of each particlecomprising the glass-ceramic, and contains not more than 10 percent byweight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, basedon the total weight of the amorphous material of each particle of theportion, wherein the glass-ceramic of at least some of the particles hasx, y, and z dimensions each perpendicular to each other, and whereineach of the x, y, and z dimensions is at least 25 micrometers; andgrading the abrasive particles comprising the glass-ceramic to provide aplurality of abrasive particles having a specified nominal grade,wherein at least a portion of the plurality of abrasive particles is aplurality of the abrasive particles comprising the glass-ceramic.
 27. Amethod for making abrasive particles, the method comprising:heat-treating ceramic comprising an amorphous material such that atleast a portion of the amorphous material is converted to aglass-ceramic, wherein the amorphous material comprises Al₂O₃, at least15 percent by weight ZrO₂, based on the total weight of the amorphousmaterial, and contains not more than 10 percent by weight collectivelyAs₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weightof the amorphous material, wherein the amorphous material has x, y, andz dimensions each perpendicular to each other, and wherein each of thex, y, and z dimensions is at least 25 micrometers, wherein theglass-ceramic comprises the Al₂O₃, the at least 15 percent by weightZrO₂, based on the total weight of the glass-ceramic, and contains notmore than 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅,SiO₂, TeO₂, and V₂O₅, based on the total weight of the glass-ceramic,wherein the glass-ceramic has x, y, and z dimensions each perpendicularto each other, and wherein each of the x, y, and z dimensions is atleast 25 micrometers; crushing the glass-ceramic to provide abrasiveparticles comprising the glass-ceramic; and grading the abrasiveparticles comprising the glass-ceramic to provide a plurality ofabrasive particles having a specified nominal grade, wherein at least aportion of the plurality of abrasive particles is a plurality of theabrasive particles comprising the glass-ceramic.
 28. A method ofabrading a surface, the method comprising: providing an abrasive articlecomprising a binder and a plurality of abrasive particles, wherein atleast a portion of the abrasive particles is a plurality of abrasiveparticles comprising a glass-ceramic, wherein the glass-ceramiccomprises Al₂O₃, at least 15 percent by weight ZrO₂, based on the totalweight of the glass-ceramic of each particle of the portion, and Y₂O₃,wherein at least a portion of the Y₂O₃ is present as at least onedistinct crystalline phase; contacting at least one of the abrasiveparticles comprising the glass-ceramic with a surface of a workpiece;and moving at least one of the contacted abrasive particles comprisingthe glass-ceramic or the contacted surface to abrade at least a portionof the surface with the contacted abrasive particles comprising theglass-ceramic.
 29. A method of abrading a surface, the methodcomprising: providing an abrasive article comprising a binder and aplurality of abrasive particles, wherein at least a portion of theabrasive particles is a plurality of abrasive particles comprising aglass-ceramic, wherein the glass-ceramic comprises Al₂O₃, at least 15percent by weight ZrO₂, based on the total weight of the glass-ceramicof each particle of the portion, and REO, wherein at least a portion ofthe REO is present as at least one distinct crystalline phase;contacting at least one of the abrasive particles comprising theglass-ceramic with a surface of a workpiece; and moving at least one ofthe contacted abrasive particles comprising the glass-ceramic or thecontacted surface to abrade at least a portion of the surface with thecontacted abrasive particles comprising the glass-ceramic.
 30. A methodof abrading a surface, the method comprising: providing an abrasivearticle comprising a binder and a plurality of abrasive particles,wherein at least a portion of the abrasive particles is a plurality ofabrasive particles comprising a glass-ceramic, wherein the glass-ceramiccomprises Al₂O₃, at least 15 percent by weight ZrO₂, based on the totalweight of the glass-ceramic of each particle comprising theglass-ceramic of each particle of the portion, and contains not morethan 10 percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂,TeO₂, and V₂O₅, based on the total weight of the glass-ceramic of eachparticle comprising the glass-ceramic of each particle of the portion,wherein the glass-ceramic of at least some of the particles has x, y,and z dimensions each perpendicular to each other, and wherein each ofthe x, y, and z dimensions are at least 25 micrometers; contacting atleast one of the abrasive particles comprising the glass-ceramic with asurface of a workpiece; and moving at least one of the contactedabrasive particles comprising the glass-ceramic or the contacted surfaceto abrade at least a portion of the surface with the contacted abrasiveparticles comprising the glass-ceramic.
 31. A method of abrading asurface, the method comprising: providing an abrasive article comprisinga binder and a plurality of abrasive particles, wherein at least aportion of the abrasive particles is a plurality of abrasive particlescomprising a glass-ceramic, wherein the glass-ceramic comprises Al₂O₃,ZrO₂, and a metal oxide other than Al₂O₃ or ZrO₂, wherein at least aportion of the metal oxide other than Al₂O₃ or ZrO₂ is present as atleast one distinct crystalline phase, wherein the glass-ceramic of eachparticle of the portion collectively comprises at least 50 percent byweight collectively of the Al₂O₃ and the ZrO₂, based on the total weightof the glass-ceramic, wherein the glass-ceramic of each particle of theportion contains not more than 20 percent by weight collectively As₂O₃,B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, based on the total weight of theglass-ceramic, wherein the glass-ceramic of at least some of the portionof abrasive particles has x, y, and z dimensions each perpendicular toeach other, and wherein each of the x, y, and z dimensions are at least25 micrometers; contacting at least one of the abrasive particlescomprising the glass-ceramic with a surface of a workpiece; and movingat least one of the contacted abrasive particles comprising theglass-ceramic or the contacted surface to abrade at least a portion ofthe surface with the contacted abrasive particles comprising theglass-ceramic.
 32. Amorphous material comprising Al₂O₃, ZrO₂, and ametal oxide other than Al₂O₃ or ZrO₂, wherein at least a portion of themetal oxide other than Al₂O₃ or ZrO₂ forms a distinct crystalline phaseif the amorphous material is crystallized, wherein the amorphousmaterial comprises at least 50 percent by weight collectively of theAl₂O₃ and the ZrO₂, based on the total weight of the amorphous material,wherein the amorphous material contains not more than 20 percent byweight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, and V₂O₅, basedon the total weight of the amorphous material, wherein the amorphousmaterial has x, y, and z dimensions each perpendicular to each other,wherein each of the x, y, and z dimensions is at least 25 micrometers,and wherein the amorphous material does not have a T_(g).
 33. Theamorphous material according to claim 32 comprising at least 35 percentby weight Al₂O₃, based on the total weight of the amorphous material.34. The amorphous material according to claim 32 comprising Al₂O₃ in arange of about 55 to about 65 percent by weight to a range of about 45to about 35 percent by weight ZrO₂, based on the total Al₂O₃ and ZrO₂content of the amorphous material.
 35. The amorphous material accordingto claim 32 wherein the metal oxide other than Al₂O₃ or ZrO₂ is TiO₂.36. Ceramic comprising the amorphous material according to claim
 32. 37.The ceramic according to claim 32 wherein the amorphous material isglass.
 38. A method for making amorphous material comprising Al₂O₃,ZrO₂, and a metal oxide other than Al₂O₃ or ZrO₂, wherein at least aportion of the metal oxide other than Al₂O₃ or ZrO₂ forms a distinctcrystalline phase if the amorphous muterial is crystallized, wherein theamorphous material comprises at least 50 percent by weight collectivelyof the Al₂O₃ and the ZrO₂, based on the total weight of the amorphousmaterial, wherein the amorphous material contains not more than 20percent by weight collectively As₂O₃, B₂O₃, GeO₂, P₂O₅, SiO₂, TeO₂, andV₂O₅, based on the total weight of the amorphous material, wherein theumorphous material has x, y, and z dimensions each perpendicular to eachother, wherein each of the x, y, and z dimensions is at least 25micrometers, and wherein the amorphous material does not have a T_(g),the method comprising: melting sources of at least Al₂O₃, ZrO₂, and ametal oxide other than Al_(2 O) ₃ or ZrO₂ to provide a melt; cooling themelt to provide the amorphous material.
 39. Amorphous material accordingto claim 1 in the form of an IR window.
 40. Glass-ceramic according toclaim 9 in the form of an IR window.
 41. Amorphous material according toclaim 32 in the form of an IR window.